from:"\"dave\""

On Saturday, September 21, 2019 at 2:46:15 PM UTC-4, boB Stepp wrote:
> On Sat, Sep 21, 2019 at 1:01 PM Dave Martin  wrote:
> >
> > On Saturday, September 21, 2019 at 1:33:12 PM UTC-4, Terry Reedy wrote:
> > > On 9/21/2019 11:53 AM, Dave Martin wrote:
> [...]
> > > > #get the combined data and load the fits files
> > > >
> > > > fits_filename="Gaia_DR2/gaiadr2_100pc.fits"
> > > > df=pd.DataFrame()
> > > > with fits.open(fits_filename) as data:
> > > > df=pd.DataFrame(data[1].data)
> > >
> > > A 'with' statement is a compound statement.  It must be followed by a
> > > 'suite', which usually consists of an indented block of statements.
> > > This is line 17 from the first non-blank line you posted.
> [...]
> 
> > Can you provide an example of how to use the suite feature. Thank you.
> 
> Dave, you seem to have some expectation that you should be given the
> answer.  That is not how help is given in this forum.  You are
> expected to be doing the needed to work before being helped further.
> You have been referred to the tutorial multiple times.  Please read
> it!  Indentation is so fundamental to structuring Python code that it
> is clear that you need grounding in Python fundamentals.  Otherwise
> you are essentially Easter-egging through a code sample that you have
> no true understanding of.
> 
> If you must continue to Easter-egg Python instead of reading the
> tutorial (or something equivalent) then check the section of the
> tutorial on files.  You will find examples of the use of "with" there.
> 
> 
> -- 
> boB
Bob,
You seem to have the expectation that you know more about coding than me and 
that you can insult me without me retaliating. If I were you, I would leave 
this forum and never respond to another person question again, if you think 
that you can rudely ransack your way through what is supposed to be a helpful 
tool.

-Dave
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Python shows error on line 15 that i cant fix

On Saturday, September 21, 2019 at 1:33:12 PM UTC-4, Terry Reedy wrote:
> On 9/21/2019 11:53 AM, Dave Martin wrote:
> > 
> > # starAbsMags=df['radial_velocity']
> > 
> > #GaiaPandasEscapeVelocityCode
> > 
> > import pandas as pd
> > import numpy as np
> > from astropy.io import fits
> > import astropy
> > import matplotlib.pyplot as plt
> > 
> > 
> > #get the combined data and load the fits files
> > 
> > fits_filename="Gaia_DR2/gaiadr2_100pc.fits"
> > df=pd.DataFrame()
> > with fits.open(fits_filename) as data:
> > df=pd.DataFrame(data[1].data)
> 
> A 'with' statement is a compound statement.  It must be followed by a 
> 'suite', which usually consists of an indented block of statements.
> This is line 17 from the first non-blank line you posted.
> 
> Please stop spamming the list with multiple posts.  Do spend a few hours 
> reading the tutorial until you understand my answer.
> https://docs.python.org/3/tutorial/index.html  Also read 
> https://stackoverflow.com/help/minimal-reproducible-example
> so you can ask better questions.
> 
> I presume you got "SyntaxError: expected an indented block".
> A minimal example getting this error is, for instance,
> 
> while True:
> a = 1
> 
> -- 
> Terry Jan Reedy

Can you provide an example of how to use the suite feature. Thank you. 
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: python is bugging

On Saturday, September 21, 2019 at 12:44:27 PM UTC-4, Brian Oney wrote:
> On Sat, 2019-09-21 at 08:57 -0700, Dave Martin wrote:
> > On Saturday, September 21, 2019 at 11:55:29 AM UTC-4, Dave Martin
> > wrote:
> > > what does expected an indented block
> > 
> > *what does an indented block mean?
> 
> It means that the line of code belongs to a certain body as defined
> above its position.  
> 
> Please follow the tutorial.
> 
> https://docs.python.org/3/tutorial/index.html

df.to_csv(r"faststars.csv", index=None,header=True)
# starAbsMags=df['radial_velocity']

#GaiaPandasEscapeVelocityCode

import pandas as pd
import numpy as np
from astropy.io import fits
import astropy
import matplotlib.pyplot as plt


#get the combined data and load the fits files

fits_filename="Gaia_DR2/gaiadr2_100pc.fits"
df=pd.DataFrame()
with fits.open(fits_filename) as data:
df=pd.DataFrame(data[1].data)
df.columns=[c.lower() for c in df.columns]
print("Columns.")
print(df.columns.values)
print("n/n")
#print out some data meta info to see what we're working with
print("Number of stars:")
nstars=len(df)
print(nstars)
distances = (df['parallax']/1000)
starAbsMags =df['phot_g_mean_mag']
df = df[(df.parallax_over_error > 10 ) ]
print("Left after filter: " +str(len(df)/float(nstars)*100)+" %")
df.hist(column='radial_velocity')
#fastdf=df[(df.radial_velocity > 200) | (df.radial_velocity < -200)]
fastdf=df[(df.radial_velocity > 550)|(df.radial_velocity<-550)]
print(len(fastdf))
#print(fastdf)# starTemps=df['astrometric_weight_al']
# df.plot.scatter("radial_velocity", "astrometric_weight_al", s=1, 
c="radial_velocity", colormap="plasma")
# #df=df[(df.radial_velocity>=-550)]
# #plt.axis([0,400,-800,-550])
# #plt.axis([0,400,550,800])
# plt.xlabel('weight(Au)')
# plt.ylabel('Speed')
# plt.title('Gaia Speed vs Weight')

this is my code the error is on line 15
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: python is bugging

On Saturday, September 21, 2019 at 11:55:29 AM UTC-4, Dave Martin wrote:
> what does expected an indented block

*what does an indented block mean?
-- 
https://mail.python.org/mailman/listinfo/python-list

python is bugging

what does expected an indented block
-- 
https://mail.python.org/mailman/listinfo/python-list

Python shows error on line 15 that i cant fix



# starAbsMags=df['radial_velocity']

#GaiaPandasEscapeVelocityCode

import pandas as pd
import numpy as np
from astropy.io import fits
import astropy
import matplotlib.pyplot as plt


#get the combined data and load the fits files

fits_filename="Gaia_DR2/gaiadr2_100pc.fits"
df=pd.DataFrame()
with fits.open(fits_filename) as data:
df=pd.DataFrame(data[1].data)
df.columns=[c.lower() for c in df.columns]
print("Columns.")
print(df.columns.values)
print("n/n")
#print out some data meta info to see what we're working with
print("Number of stars:")
nstars=len(df)
print(nstars)
distances = (df['parallax']/1000)
starAbsMags =df['phot_g_mean_mag']
df = df[(df.parallax_over_error > 10 ) ]
print("Left after filter: " +str(len(df)/float(nstars)*100)+" %")
df.hist(column='radial_velocity')
#fastdf=df[(df.radial_velocity > 200) | (df.radial_velocity < -200)]
fastdf=df[(df.radial_velocity > 550)|(df.radial_velocity<-550)]
print(len(fastdf))
#print(fastdf)# starTemps=df['astrometric_weight_al']
# df.plot.scatter("radial_velocity", "astrometric_weight_al", s=1, 
c="radial_velocity", colormap="plasma")
# #df=df[(df.radial_velocity>=-550)]
# #plt.axis([0,400,-800,-550])
# #plt.axis([0,400,550,800])
# plt.xlabel('weight(Au)')
# plt.ylabel('Speed')
# plt.title('Gaia Speed vs Weight')

-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Formatting floating point

2019-09-04 Thread Dave via Python-list


On 9/4/19 1:38 PM, Rhodri James wrote:

On 04/09/2019 18:12, Dave via Python-list wrote:
My question is why, and where do I find a reliable source of 
information on formatting numbers?  Not interested in replacement 
values like '{} {}'.format(1, 2).


Here: 
https://docs.python.org/3/library/string.html#format-specification-mini-language 



I suspect the thing you were overlooking was that format() expects to be 
given a format specification, and you gave it a format string.  Instead 
of format(num, "{0:.1f}"), you wanted format(num, ".1f").  If you had 
tried "{0:.1f}".format(num) instead, you would have found that worked too.



Thanks Rhodri

Dave,
--
https://mail.python.org/mailman/listinfo/python-list

Re: Formatting floating point

2019-09-04 Thread Dave via Python-list


On 9/4/19 1:25 PM, Chris Angelico wrote:

On Thu, Sep 5, 2019 at 3:16 AM Dave via Python-list
 wrote:


All,

I have been going in circles trying to format a floating point number so
there is only 1 decimal place.  In reading all of the gobble-gook that
passes for Python advice, it looked like I should have done this:

numStr = '3.14159'
num = float(numstr) # OK so far
numFmt = format(num, '{0:.1f}') # Errors on format string
# --- Alternative that also does not work
numFmt = float("{0:.1f}".format(numStr))
# ---
numFmt = format(num, '0.1f')# Does work



Let's start by eliminating a few possibilities here. Don't try
formatting the original string, and don't call float() on the result
afterwards; just start with a floating-point value, and then create a
formatted string. If you think about starting with a value (which in
this case is a number) and the need to make a displayable version
(which implies that it's a string), your options basically look like
this:

num = 3.14159
num_fmt = format(num, ".1f")
num_fmt = "{0:.1f}".format(num)
num_fmt = f"{num:.1f}"

All of these will give you back the string "3.1". All of them involve
a format string of ".1f", and they differ only in how they're choosing
which value to put there.

Hopefully that will clear things up a bit.

ChrisA



That helps!  Thanks Chris.

Dave,
--
https://mail.python.org/mailman/listinfo/python-list

Formatting floating point

2019-09-04 Thread Dave via Python-list


All,

I have been going in circles trying to format a floating point number so 
there is only 1 decimal place.  In reading all of the gobble-gook that 
passes for Python advice, it looked like I should have done this:


numStr = '3.14159'
num = float(numstr) # OK so far
numFmt = format(num, '{0:.1f}') # Errors on format string
# --- Alternative that also does not work
numFmt = float("{0:.1f}".format(numStr))
# ---
numFmt = format(num, '0.1f')# Does work

My question is why, and where do I find a reliable source of information 
on formatting numbers?  Not interested in replacement values like '{} 
{}'.format(1, 2).


Thanks,
Dave

--
https://mail.python.org/mailman/listinfo/python-list

Re: Application Preferences

2019-08-19 Thread Dave via Python-list


On 8/19/19 1:53 PM, Barry Scott wrote:




On 19 Aug 2019, at 13:43, Dave via Python-list  wrote:

The plan for an app that I'm doing was to use SQLite for data and to hold the 
preference settings as some apps do.  The plan was changed last week to allow 
the user to select the location of the data files (SQLite) rather than putting 
it where the OS would dictate.  Ok with that, but it brings up some questions.  
First, I will need to have a file that points to the location of the data file  
since that can't be hard coded. Second, if I have to have a file that is likely 
part of the application group of files, would it make more sense to use a more 
traditional preferences file?  How have other Python app developers done in 
this case?


There are expected locations for config files and data files on each OS.

On macOS you would use ~/Library/Preferences/ and put a file or a folder of 
files in there.
The convention is use your website name as the base name of the  file or folder.
For example for scm-workbench I use: org.barrys-emacs.scm-workbench as the 
folder name for
all the scm-workbench files.

On Windows you can use a file or folder in %APPDATA% that is named after your 
app. You should
find the folder by doing a win32 API call to get the value. See 
getPreferencesDir()  in
https://github.com/barry-scott/scm-workbench/blob/master/Source/Common/wb_platform_win32_specific.py
 
<https://github.com/barry-scott/scm-workbench/blob/master/Source/Common/wb_platform_win32_specific.py>
for how to get the value.

On Linux the XDG spec says that you should put config files in 
~/.config/ and data files
in  ~/.local/share/. Doing XDG to the spec is a little involved. I 
have some experimental
code that implements the logic for config the XdgConfigPath class in:
https://github.com/barry-scott/CLI-tools/blob/master/Source/smart_find/__init__.py 
<https://github.com/barry-scott/CLI-tools/blob/master/Source/smart_find/__init__.py>

Putting a file directly in the $HOME folder is no longer recommended.

The format of the config data you are free to choose.
I have been using JSON files recently as it allow for structured data.


Barry



Barry, and all,

I agree that various OS's have a favorite place to put things.  Python 
has a library that will help.  However, there are valid reasons to let 
the customer choose.  Perhaps the drive/folder is a journaling one, or 
one that is backed up multiple times per day.  My take is to start with 
the OS solution, but let the customer decide.


How did this thread show up in the SQLite mailing list anyway?  Really 
has nothing to do with SQLite that I can see.


Dave,


--
https://mail.python.org/mailman/listinfo/python-list

Re: Application Preferences

2019-08-19 Thread Dave via Python-list


On 8/19/19 9:22 AM, Malcolm Greene wrote:

Hi Dave,


The plan for an app that I'm doing was to use SQLite for data and to hold the 
preference settings as some apps do.  The plan was changed last week to allow 
the user to select the location of the data files (SQLite) rather than putting 
it where the OS would dictate.  Ok with that, but it brings up some questions.  
First, I will need to have a file that points to the location of the data file  
since that can't be hard coded. Second, if I have to have a file that is likely 
part of the application group of files, would it make more sense to use a more 
traditional preferences file?  How have other Python app developers done in 
this case?


We handle the "where is my config file" question by defaulting to script's 
current directory, then a script-specific folder within their home directory. Users can 
override that behavior by setting a script specific environment variable or by using a 
command line switch to point to a different location or config file.

We store our preferences in an INI style config file which we've found easier 
to support when there's problems.

Malcolm



Malcolm,

Thanks for the reply.  I agree that a traditional INI file is the 
easiest way, especially since Python supports them.  So if I understand 
you, your apps look like this:


-App Dir
  |
  +-App Code Folder
 |
 +-(File to direct to home folder)

-Home Folder (the default location, but user can select other locations)
  |
  +-App INI Folder
 |
 +-App INI file
--
https://mail.python.org/mailman/listinfo/python-list

Application Preferences

2019-08-19 Thread Dave via Python-list

The plan for an app that I'm doing was to use SQLite for data and to 
hold the preference settings as some apps do.  The plan was changed last 
week to allow the user to select the location of the data files (SQLite) 
rather than putting it where the OS would dictate.  Ok with that, but it 
brings up some questions.  First, I will need to have a file that points 
to the location of the data file  since that can't be hard coded. 
Second, if I have to have a file that is likely part of the application 
group of files, would it make more sense to use a more traditional 
preferences file?  How have other Python app developers done in this case?


Thanks,
Dave
--
https://mail.python.org/mailman/listinfo/python-list

Re: Create multiple sqlite tables, many-to-many design


On 8/13/19 5:46 PM, Rich Shepard wrote:

On Tue, 13 Aug 2019, Rich Shepard wrote:


Read Joe Celko's books, starting with his SQL Programming Guide, then SQL


That should be SQL Programming Style

Rich


Rich,

On my next trip to BN I'll see if they have them.  That is long term 
though.  Right now I just need to know how to populate the join table 
and anything else that has escaped me.


SQL is cool.  SQL + Python (or C or C++ or Java) is more cool.  Lot 
easier to understand than pointer math in C.


Dave,
--
https://mail.python.org/mailman/listinfo/python-list

Re: Create multiple sqlite tables, many-to-many design


On 8/13/19 2:59 PM, Chris Angelico wrote:

On Wed, Aug 14, 2019 at 4:50 AM Dave via Python-list
 wrote:

Some of the tables are related.  For example:

Hiking_Table Trails_TableJoining_Table
--
hike_id PK   trail_id  PKhike_id   FK
hike_date  TEXT  trail_name  TEXTtrail_id   FK
hike_destination TEXTtrail_rating REAL
hike_rating  REALtrail_comments TEXT
hike_comments  TEXT

So far, so good.  I know how to create the tables.  What I am struggling
with is how do I insert data into the joining table or don"t I?  If so,
do I need to query the other two tables to get the auto-number ID's?
Some things I have read suggest that the joining table just contains
references, so there is no actual insert.  A pointer to information how
to do this would be appreciated.  As for queries, I think I use joins,
but a pointer on how to do this would also be appreciated.


The joining table is a real thing, and will have real inserts. It
might be easier to think of this as two separate one-to-many
relationships; for the sake of demonstration, I'm going to add another
column to your joining table.

hike_sections ==> hike_id references hikes, trail_id references
trails, companion_name

You've decided to have someone with you for some sections of your
hike. As such, what we have is a number of "mini-hikes" that make up a
single hike (that's a one-to-many relationship between hikes and
sections), and also a single trail can be a section of any number of
hikes (so, another one-to-many relationship between trails and
sections). For any given section, there is exactly one companion.

Does this make the many-to-many relationship a bit easier to
understand? It'll work exactly the same way even if you have no
ancillary information in that joining table.

ChrisA


Chris,

Thanks for the note.  I get the theory of MTM and the join table.  It is 
the implementation I don't get.  Let me see if I can demonstrate my 
confusion using pseudo code.


def dbTables_create (dbpath):

sql_HikeTable = """ CREATE TABLE IF NOT EXISTS hike (
hike_id INTEGER AUTO_INCREMENT PRIMARY KEY,
hike_date TEXT,
hike_destination TEXT,
hike_rating REAL,
hike_comments TEXT ) """

sql_TrailTable = """ CREATE TABLE IF NOT EXISTS trail (
trail_id INTEGER AUTO_INCREMENT PRIMARY KEY,
trail_name TEXT,
trail_rating REAL,
trail_comment TEXT ) """

sql_JoiningTable = """ CREATE TABLE IF NOT EXISTS hike_trail (
hike_id INTEGER
trail_id INTEGER ) """

# Some more code to open connection, create cursor, execute SQL.

def getUserInput ():
# Code to get the user input.
# The user input is:
hdate = "2019-05-28"
hdestination = "Top of White Face Mountain, NY."
hrating = 5.0   # Rating scale 1.0 (bad) to 5.0 (perfect).
hcomments "Got to do again.  Better shoes needed."
tname1 = "Brookside"
trating1 = 4.5
tcomments1 = "Easy"
tname2 = "Wilmington Trail"
trating2 = 4.9
tcomments2 = "Awesome!!"

def dbDataInsert():

sql_HikeInsert = """ INSERT INTO hike (
 hike_date,
 hike_destination,
 hike_rating,
 hike_comments )
 VALUES (
 hdate,
 hdestination,
 hrating,
 hcomments ) """

sql_TrailInsert = """ NSERT INTO trail (
 trail_name,
 trail_rating,
 trail_comment )
  VALUES (
 tname1,
 trating1,
 tcomments1 ) """

sql_TrailInsert = """ NSERT INTO trail (
 trail_name,
 trail_rating,
 trail_comment )
  VALUES (
 tname2,
     trating2,
 tcomments2 ) """

""" ---> Now what?  I need to populate the join (hike_trail) table.
 Do I query the tables to get the id's?  Is there another
 way?  This is the part I really don't get.  """

Dave,


--
https://mail.python.org/mailman/listinfo/python-list

Re: Create multiple sqlite tables, many-to-many design


On 8/13/19 4:45 PM, MRAB wrote:

On 2019-08-13 19:59, Chris Angelico wrote:

On Wed, Aug 14, 2019 at 4:50 AM Dave via Python-list
 wrote:

Some of the tables are related.  For example:

Hiking_Table Trails_Table    Joining_Table
-        -
hike_id PK   trail_id  PK    hike_id   FK
hike_date  TEXT  trail_name  TEXT    trail_id   FK
hike_destination TEXT    trail_rating REAL
hike_rating  REAL    trail_comments TEXT
hike_comments  TEXT

So far, so good.  I know how to create the tables.  What I am struggling
with is how do I insert data into the joining table or don"t I?  If so,
do I need to query the other two tables to get the auto-number ID's?
Some things I have read suggest that the joining table just contains
references, so there is no actual insert.  A pointer to information how
to do this would be appreciated.  As for queries, I think I use joins,
but a pointer on how to do this would also be appreciated.


The joining table is a real thing, and will have real inserts. It
might be easier to think of this as two separate one-to-many
relationships; for the sake of demonstration, I'm going to add another
column to your joining table.

hike_sections ==> hike_id references hikes, trail_id references
trails, companion_name

You've decided to have someone with you for some sections of your
hike. As such, what we have is a number of "mini-hikes" that make up a
single hike (that's a one-to-many relationship between hikes and
sections), and also a single trail can be a section of any number of
hikes (so, another one-to-many relationship between trails and
sections). For any given section, there is exactly one companion.

Does this make the many-to-many relationship a bit easier to
understand? It'll work exactly the same way even if you have no
ancillary information in that joining table.

Might I also suggest dropping unnecessary prefixes from the field names. 
For example, "hike_comments" in "Hiking_Table" can be called just 
"comments" because it's clear from the context that a field called 
"comments" in the hiking table will contain comments about hiking, if 
you see what I mean.


I do indeed.  I did that so it was easy for everyone to follow.  Having 
started with assm. and C, I have to remind myself to be more explanatory 
in naming.  Guess I over-did it.  The actual code is different. htbl, 
ttbl, jtbl, etc.  Too short?


Dave,
--
https://mail.python.org/mailman/listinfo/python-list

Create multiple sqlite tables, many-to-many design


Oops!  Just posted this to the wrong newsgroup.  Sorry!!!


I'm doing a Python app that uses SQLite, and am stumbling on a few 
questions.  I've read a lot of books and documentation, but two 
questions still allude me.  Hope someone that been there done this can 
help.  Below is a note I sent to the SQLite mailing list yesterday.  So 
far, nothing.  Need to get going, so many thanks!


I'm doing an app. that uses sqlite, and has a many-to-many relationship. 
 The areas I need some guidance are:

* Best way to create multiple tables the first time the app. is started.
* How to create a MTM relationship and add/modify data.

I can create tables (Python) by putting the code in discrete functions 
for each table and passing just the path to the database.  I can also 
create a calling function that gets a connection and passes that.  What 
is the pro-con of each since each seems to work?  Better ideas?


Some of the tables are related.  For example:

Hiking_Table Trails_TableJoining_Table
--
hike_id PK   trail_id  PKhike_id   FK
hike_date  TEXT  trail_name  TEXTtrail_id   FK
hike_destination TEXTtrail_rating REAL
hike_rating  REALtrail_comments TEXT
hike_comments  TEXT

So far, so good.  I know how to create the tables.  What I am struggling 
with is how do I insert data into the joining table or don"t I?  If so, 
do I need to query the other two tables to get the auto-number ID's? 
Some things I have read suggest that the joining table just contains 
references, so there is no actual insert.  A pointer to information how 
to do this would be appreciated.  As for queries, I think I use joins, 
but a pointer on how to do this would also be appreciated.


Thanks,
Dave
--
https://mail.python.org/mailman/listinfo/python-list

Python/SQLite best practices

2019-08-05 Thread Dave via Python-list

I'm looking for some tips from experienced hands on on this subject. 
Some of the areas of interest are (feel free to add more):


* Passing connections and cursors - good, bad indifferent?  I try to 
avoid passing file handles unless necessary, so I view connections and 
cursors the same.  Though that said, I'm not aware of any specific 
problems in doing so.


For designs with multiple tables:
* Better to pass an sql string to functions that create/add 
data/update/delete data and pass them to create, insert, update, delete 
functions; or have those functions for each table?  Taking table 
creation for example, if there are five tables, and the sql string is 
passed, there would need to be six functions to do it, though the 
complexity of each function may be reduced a little.  [table1create with 
sql and establishing a cursor, to table5create and then a function that 
executes the sql].


Best way to establish the connection and cursor, as well as close them? 
I have seen many ways to do this, and know that the with block can be 
used to create a connection and close it automatically, but the same is 
not true of the cursor.  Also, using only a with block does not handle 
any errors as well as a try/with.  For example:


|   try:
|   # Use with block to create connection – it will close self.
|   with sqlite3.connect(path) as conn:
|   cur = conn.cursor()
|   cur.execute(sql_ProjectsTable)
|   cur.close()
|   except Error as e:
|   print(e)

What else?

Dave,
--
https://mail.python.org/mailman/listinfo/python-list

Re: Python best practice instantiating classes in app

2019-04-29 Thread Dave


On 4/29/19 3:26 PM, Terry Reedy wrote:

On 4/29/2019 1:38 PM, Dave wrote:
As apps get more complex we add modules, or Python files, to organize 
things.  One problem I have is a couple of data classes (list of 
dictionary objects) in a few modules that are used in a number of the 
other modules.  For example a list of meter reading dictionaries in 
one module is used by the user interface module to get the data from 
the user, a report module to display the data, and a file module to 
save and retrieve the data to/from file.  All the modules need to use 
the same instance of the list classes.



There are a number of ways to do this.  One is a module that creates 
the objects, then import that module into all of the others.  Works well, 


You can have one *or more* such modules.  Perhaps you already do.


but may not be the best way to do the job.


In what way do you consider it unsatisfactory.


It is not that I consider it unsatisfactory as much as I'm looking for 
the best way.  I am constantly amazed at the thought that has been given 
to this language (with the exception of access modifiers - perhaps, and 
lack of a case statement), and often find that there is a better way of 
doing everything.






A slight variation is to do this in the main module, but the main 
module has to be imported into the others.


Avoid import loops unless really necessary.  They often work, but when 
they don't ... its a pain.


  Since I use the main module as a calling module to load data, start 
the user interface, and to close things down, it may not be the best 
place to also create the classes.


Another way to do this is have a line in each module to check the 
name. If it is the module name, then create the class and then import 
these modules in all the others.  A tad messy and maybe a little 
confusing.


Right.




--
https://mail.python.org/mailman/listinfo/python-list

Python best practice instantiating classes in app

2019-04-29 Thread Dave

As apps get more complex we add modules, or Python files, to organize 
things.  One problem I have is a couple of data classes (list of 
dictionary objects) in a few modules that are used in a number of the 
other modules.  For example a list of meter reading dictionaries in one 
module is used by the user interface module to get the data from the 
user, a report module to display the data, and a file module to save and 
retrieve the data to/from file.  All the modules need to use the same 
instance of the list classes.


There are a number of ways to do this.  One is a module that creates the 
objects, then import that module into all of the others.  Works well, 
but may not be the best way to do the job.


A slight variation is to do this in the main module, but the main module 
has to be imported into the others.  Since I use the main module as a 
calling module to load data, start the user interface, and to close 
things down, it may not be the best place to also create the classes.


Another way to do this is have a line in each module to check the name. 
If it is the module name, then create the class and then import these 
modules in all the others.  A tad messy and maybe a little confusing.


So what are the suggestions from people that have been down this road 
before?


Thanks,
Dave
--
https://mail.python.org/mailman/listinfo/python-list

Re: How call method from a method in same class?

2019-04-01 Thread Dave


On 4/1/19 10:29 PM, Cameron Simpson wrote:

On 01Apr2019 22:02, Dave  wrote:
As classes get more complex, it is good to call a function to do some 
of the processing, and make the code easier to follow.  My question is 
how to do that?  I've attached some silly code to illustrate the 
point.  The error is: name 'validScale' is not defined.  Well, yes it 
is, but maybe not the correct way.  Suggestions?


It is and it isn't. See below:


class TempConverter():
   """ Temperature Converter converts a tempeature from one scale
   to another scale.  For example: 32, F, C will return
   0 degrees C
   """

[...]

   def validScale(self, scaleName):
   if scaleName.upper == 'F' or 'C' or 'K':
   return True
   else:
   return False

   def convertTemp(self):
   """ Converts temperature scale if scales valid."""
   if validScale(self.scale):
   scaleValid = True

[...]

It is an instance method, so:

    if self.validScale(self.scale)

would resolve the name. However, there are several things worth 
discussing here.


First up, validScale itself returns a Boolean, so just return the test 
result. Change:


    if scaleName.upper == 'F' or 'C' or 'K':
    return True
    else:
    return False

into:

    return scaleName.upper == 'F' or 'C' or 'K'

Second, the condition is buggy. You want this:

    return scaleName.upper() in ('F', 'C', 'K')

i.e. you need to call (the "()") the .upper method, and you need to 
check if the result is in your collection of valid results.


This expression:

    value == A or B or C

means: True if value == A, otherwise B if B is true, otherwise C.

The next thing to observe is that you're testing whether self.scale is 
valid. Normal practice would be to make that test in __init__, and raise 
a ValueError if it is not so:


    def __init__(self, .scale...):
  if scale.upper() not in ('F', 'C', 'K'):
    raise ValueError("invalid scale %r: expected one of F, C or K" % 
(scale,))
why recite the scale in the message? Because it makes the offending 
value obvious. In particular, if for example you called this incorrectly 
and had the temperature in there instead of the scale that will be 
trivial to debug from the message.


Of course, you actually want to be able to test any scal evalue for 
validity, not just the one stuffed into your instance (.scale). So lets 
revisit the validScale method:


    def validScale(self, scale):
  return scaleName.upper() in ('F', 'C', 'K')

You'll notice that it doesn't depend in "self". Or, for that matter, the 
class. So this is a "static" method: a function defined in the class for 
conceptual clarity, but not with any dependence on the class itself or a 
particular class instance. So:


    @staticmethod
    def validScale(scale):
  return scaleName.upper() in ('F', 'C', 'K')

In __init__, and elsewhere, you can still call this from the instance:

    def __init__(self, .scale...):
  if not self.validScale(scale):
    raise ValueError("invalid scale %r: expected one of F, C or K" % 
(scale,))
You can also call this from _outside_ the class, for example for other 
validation:


    scale = input("Enter a temperate scale name (F, C or K): ")
    if not TempConverter.validScale(scale):
  print("Bad! Bad user!")


   newScaleValid = True


Again, validScale returns a Boolean. So you could have just gone:

    newScaleValid = self.validScale(newScale)


   if scaleValid and newScaleValid:
   print('Scale converted')
   else:
   msg = "There was and error with the scales entered.\n"
   msg = msg + "You entered: " + self.scale
   msg = msg + ' ' 'and' + self.newScale
   print(msg)

if __name__ == "__main__":
   myclass = TempConverter(32, 'f', 'c')
   myclass.convertTemp()


My personal inclination would be do define a Temperature class with a 
convert function to be used like this:


    temp = Temperature(32, 'f')
    tempC = temp.convert('c')

This reduces the complexity of the class and IMO makes it easier to use 
elsewhere.



BTW, you get an instance back from tempConverter(...), not a class. So 
don't call it "myclass".


Cheers,
Cameron Simpson 


Cameron,

I'm going to need a while to work through this.  As I mentioned, this 
was quick and dirty code just to illustrate a point - not intended to be 
good code.  So I'll take a close read tomorrow.  Thanks again!!


Dave,
--
https://mail.python.org/mailman/listinfo/python-list

Re: How call method from a method in same class?

2019-04-01 Thread Dave


On 4/1/19 10:02 PM, Dave wrote:
As classes get more complex, it is good to call a function to do some of 
the processing, and make the code easier to follow.  My question is how 
to do that?  I've attached some silly code to illustrate the point.  The 
error is: name 'validScale' is not defined.  Well, yes it is, but maybe 
not the correct way.  Suggestions?


Dave,

class TempConverter():
     """ Temperature Converter converts a tempeature from one scale
     to another scale.  For example: 32, F, C will return
     0 degrees C
     """

     def __init__(self, temperature, scale, newScale):
     self.temperature = temperature
     self.scale = scale
     self.newScale = newScale

     def validScale(self, scaleName):
     if scaleName.upper == 'F' or 'C' or 'K':
     return True
     else:
     return False

     def convertTemp(self):
     """ Converts temperature scale if scales valid."""
     if validScale(self.scale):
     scaleValid = True
     if validScale(self.newScale):
     newScaleValid = True
     if scaleValid and newScaleValid:
     print('Scale converted')
     else:
     msg = "There was and error with the scales entered.\n"
     msg = msg + "You entered: " + self.scale
     msg = msg + ' ' 'and' + self.newScale
     print(msg)

if __name__ == "__main__":
     myclass = TempConverter(32, 'f', 'c')
     myclass.convertTemp()


Thanks all for your (ready, wait for it) self-lessness help (get it?)

Dave (laughing)

--
https://mail.python.org/mailman/listinfo/python-list

Re: How call method from a method in same class?

2019-04-01 Thread Dave


On 4/1/19 10:12 PM, Irv Kalb wrote:



On Apr 1, 2019, at 7:02 PM, Dave  wrote:

As classes get more complex, it is good to call a function to do some of the 
processing, and make the code easier to follow.  My question is how to do that? 
 I've attached some silly code to illustrate the point.  The error is: name 
'validScale' is not defined.  Well, yes it is, but maybe not the correct way.  
Suggestions?

Dave,

class TempConverter():
""" Temperature Converter converts a tempeature from one scale
to another scale.  For example: 32, F, C will return
0 degrees C
"""

def __init__(self, temperature, scale, newScale):
self.temperature = temperature
self.scale = scale
self.newScale = newScale

def validScale(self, scaleName):
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False

def convertTemp(self):
""" Converts temperature scale if scales valid."""
if validScale(self.scale):
scaleValid = True
if validScale(self.newScale):
newScaleValid = True
if scaleValid and newScaleValid:
print('Scale converted')
else:
msg = "There was and error with the scales entered.\n"
msg = msg + "You entered: " + self.scale
msg = msg + ' ' 'and' + self.newScale
print(msg)

if __name__ == "__main__":
myclass = TempConverter(32, 'f', 'c')
myclass.convertTemp()
--
https://mail.python.org/mailman/listinfo/python-list



To answer your specific question, you call a method in the same class by 
calling:  self.methodName   For example:  self.validScale

However, once you fix that, you wind find that the if statement in that method 
is not built correctly.

Also, since the variable self.scale is already set in your __init__ method, 
there is no need to pass it into your function.  You could just use self.scale 
inside that method.

Irv



Irv,

Thanks for the response!  I realize the code is junk - just done to 
illustrate the problem.


Dave,
--
https://mail.python.org/mailman/listinfo/python-list

How call method from a method in same class?

2019-04-01 Thread Dave

As classes get more complex, it is good to call a function to do some of 
the processing, and make the code easier to follow.  My question is how 
to do that?  I've attached some silly code to illustrate the point.  The 
error is: name 'validScale' is not defined.  Well, yes it is, but maybe 
not the correct way.  Suggestions?


Dave,

class TempConverter():
""" Temperature Converter converts a tempeature from one scale
to another scale.  For example: 32, F, C will return
0 degrees C
"""

def __init__(self, temperature, scale, newScale):
self.temperature = temperature
self.scale = scale
self.newScale = newScale

def validScale(self, scaleName):
if scaleName.upper == 'F' or 'C' or 'K':
return True
else:
return False

def convertTemp(self):
""" Converts temperature scale if scales valid."""
if validScale(self.scale):
scaleValid = True
if validScale(self.newScale):
newScaleValid = True
if scaleValid and newScaleValid:
print('Scale converted')
else:
msg = "There was and error with the scales entered.\n"
msg = msg + "You entered: " + self.scale
msg = msg + ' ' 'and' + self.newScale
print(msg)

if __name__ == "__main__":
myclass = TempConverter(32, 'f', 'c')
myclass.convertTemp()
--
https://mail.python.org/mailman/listinfo/python-list

Re: configparser - which one?

2019-03-26 Thread Dave


On 3/26/19 4:29 AM, Terry Reedy wrote:

On 3/25/2019 8:10 PM, Dave wrote:
I use Python3 3, and expected learning how to use configparser would 
be no big deal.  Well!  Seems there is configparser, stdconfigparser, and 


configparser is what IDLE uses.  I would read the extra or deleted 
features of the others and see if they apply to your client's project.


safeconfigparser, and multiple ways to set the section and entries to 
the section.  A little confusing.  I want to future-proof may code, so 
what should I be using?


As for setting the sections and entries, the following both work.

from configparser import ConfigParser    # Python 3 syntax
parser = ConfigParser()

parser['DEFAULT'] = {'Language': 'English',
  'Units': 'English',
  'UseDefaults': 'True',
  'NumberRidesDisplay': '30',
  'Pi': '3.14'}


The dict interface is newer but I doubt that the older one will go away. 
  (IDLE uses it because it predates the dict interface.  Since this code 
is pretty static, I do not currently see a payoff for conversion.)



parser.add_section('Default')
parser.set('default', 'language', 'english')
parser.set('default', 'units_measure', 'english')
parser.set('default', 'background_color', 'white')
parser.set('default', 'useDefaults', 'true')
parser.set('default', 'numToDisp', '12')
parser.set('default', 'pi', '3.14')

The advantage of the former is that it will handle 'DEFAULT', while 
the last one won't.  I like the former, but not sure if it is the future.


We do not remove things and break backwards compatibility lightly.

Thanks everyone.  So, I'll use configparser, but I do like the 
dictionary API as it makes the code a little easier as I can pass as 
arguments a section name and a dictionary with the contents to a 
function to write the complete section.


Dave,
--
https://mail.python.org/mailman/listinfo/python-list

Re: configparser - which one?

2019-03-25 Thread Dave


On 3/25/19 10:58 PM, DL Neil wrote:

Dave,


On 26/03/19 1:10 PM, Dave wrote:
I use Python3 3, and expected learning how to use configparser would 
be no big deal.  Well!  Seems there is configparser, stdconfigparser, 
and safeconfigparser, and multiple ways to set the section and entries 
to the section.  A little confusing.  I want to future-proof may code, 
so what should I be using?



(with apologies for not answering the question directly)

After striking this problem, I was encouraged to take a look at JSON, 
and thence YAML. Once there, as they say, didn't look back!

- multi-dimensional possibilities, cf .ini
- similarity/correspondence with Python data structures
- convenient PSL
- easily adopted by (power-)users, cf Python code


WebRefs:

- similar Q: 
https://stackoverflow.com/questions/5055042/whats-the-best-practice-using-a-settings-file-in-python 



- article: https://martin-thoma.com/configuration-files-in-python/

- similar discussion: 
https://stackoverflow.com/questions/3085029/pros-and-cons-for-different-configuration-formats 



Wish I could do that.  Customer wants .ini.  I would need to sell them 
on an alternative.  The issue is human readable - .ini is easier for 
people to understand.


Dave,
--
https://mail.python.org/mailman/listinfo/python-list

configparser - which one?

2019-03-25 Thread Dave

I use Python3 3, and expected learning how to use configparser would be 
no big deal.  Well!  Seems there is configparser, stdconfigparser, and 
safeconfigparser, and multiple ways to set the section and entries to 
the section.  A little confusing.  I want to future-proof may code, so 
what should I be using?


As for setting the sections and entries, the following both work.

from configparser import ConfigParser   # Python 3 syntax
parser = ConfigParser()

parser['DEFAULT'] = {'Language': 'English',
 'Units': 'English',
 'UseDefaults': 'True',
 'NumberRidesDisplay': '30',
 'Pi': '3.14'}


parser.add_section('Default')
parser.set('default', 'language', 'english')
parser.set('default', 'units_measure', 'english')
parser.set('default', 'background_color', 'white')
parser.set('default', 'useDefaults', 'true')
parser.set('default', 'numToDisp', '12')
parser.set('default', 'pi', '3.14')

The advantage of the former is that it will handle 'DEFAULT', while the 
last one won't.  I like the former, but not sure if it is the future.


Thanks,
Dave
--
https://mail.python.org/mailman/listinfo/python-list

Re: ANN: Creating GUI Applications with wxPython

2019-02-27 Thread Dave


On 2/27/19 11:38 AM, Rhodri James wrote:

On 27/02/2019 15:37, Dave wrote:
* GUI must support all desktops with a native look and feel.  Kivy 
fails this one.  Will have mobile apps later in the year, so it would 
be nice if one GUI fits all, but am ok with 2 gui's if needed.


This requirement will cause you endless pain, particularly when mobiles 
enter the picture.  I'm not convinced it's a completely good idea; a 
sensible UI for a desktop probably won't be sensible for a phone and 
vice versa




Agreed - that is why I'm open to two GUI kits.

Dave
--
https://mail.python.org/mailman/listinfo/python-list

Re: ANN: Creating GUI Applications with wxPython

2019-02-27 Thread Dave

Sorry about the duplicate messages - bad hair day!

Dave,

On 2/27/19 10:38 AM, Dave wrote:

On 1/14/19 2:08 PM, Mike Driscoll wrote:

Hi,

I just thought I would let you all know that I am working on my 2nd
wxPython book, "Creating GUI Applications with wxPython". This one
will be about actually creating small runnable applications instead of
just recipes like my Cookbook did. I hope to have 8-10 working
applications included with the book.

You can read more about it here if you are interested:
https://www.blog.pythonlibrary.org/2019/01/14/creating-gui-applications-with-wxpython-kickstarter/

Feel free to ask me questions about it too.

Thanks,
Mike

Mike,

I have two Python 3 (3.6) apps that will get the full GUI treatment very
soon. I'm in the process of choosing a GUI, and that may be where
you/your book can help. Seems this is not a trivial effort (wishing
that Python was like VB6 from the 90's).

Anyway, here is what I am looking for - hopefully it helps guide you.

* GUI relatively easy to understand and implement. easyGUI is truly
easy in all areas, but fails some of my other requirements. The
QT/PyQT/PySide2 situation is a mess - which one to use, why, any
implementation differences, etc.

* Performance is very good. Users hate to wait - for anything!

* Lots of widgets! I'll need a spreadsheet-like widget, a form widget
to enter information on parts, activities, etc., splash screen that the
code can talk to while the app is loading, and the big one - a
cross-platform printer widget that works with Windows and Mac/Unix/CUPS.
A network widget may also be good.

* A GUI designer may be good. Currently there is Glade for GTK, and
QT-Designer for QT.

* GUI must support all desktops with a native look and feel. Kivy fails
this one. Will have mobile apps later in the year, so it would be nice
if one GUI fits all, but am ok with 2 gui's if needed.

* A great book taking me from beginner to expert.

Dave,

--
https://mail.python.org/mailman/listinfo/python-list

Re: ANN: Creating GUI Applications with wxPython

2019-02-27 Thread Dave

On 1/14/19 2:08 PM, Mike Driscoll wrote:

Hi,

I just thought I would let you all know that I am working on my 2nd wxPython book,
"Creating GUI Applications with wxPython". This one will be about actually
creating small runnable applications instead of just recipes like my Cookbook did. I hope
to have 8-10 working applications included with the book.

You can read more about it here if you are interested:
https://www.blog.pythonlibrary.org/2019/01/14/creating-gui-applications-with-wxpython-kickstarter/

Feel free to ask me questions about it too.

Thanks,
Mike

Mike,

Anyway, here is what I am looking for - hopefully it helps guide you.

* Performance is very good. Users hate to wait - for anything!

* A GUI designer may be good. Currently there is Glade for GTK, and
QT-Designer for QT.

* GUI must support all desktops with a native look and feel. Kivy fails
this one. Will have mobile apps later in the year, so it would be nice
if one GUI fits all, but am ok with 2 gui's if needed.

* A great book taking me from beginner to expert.

Dave,

--
https://mail.python.org/mailman/listinfo/python-list

Re: ANN: Creating GUI Applications with wxPython

2019-02-27 Thread Dave

On 1/14/19 2:08 PM, Mike Driscoll wrote:

Hi,

I just thought I would let you all know that I am working on my 2nd wxPython book,
"Creating GUI Applications with wxPython". This one will be about actually
creating small runnable applications instead of just recipes like my Cookbook did. I hope
to have 8-10 working applications included with the book.

You can read more about it here if you are interested:
https://www.blog.pythonlibrary.org/2019/01/14/creating-gui-applications-with-wxpython-kickstarter/

Feel free to ask me questions about it too.

Thanks,
Mike

Mike,

Anyway, here is what I am looking for - hopefully it helps guide you.

* Performance is very good. Users hate to wait - for anything!

* A GUI designer may be good. Currently there is Glade for GTK, and
QT-Designer for QT.

* GUI must support all desktops with a native look and feel. Kivy fails
this one. Will have mobile apps later in the year, so it would be nice
if one GUI fits all, but am ok with 2 gui's if needed.

* A great book taking me from beginner to expert.

Dave,

--
https://mail.python.org/mailman/listinfo/python-list

Re: ANN: Creating GUI Applications with wxPython

2019-02-27 Thread Dave

On 1/14/19 2:08 PM, Mike Driscoll wrote:

Hi,

I just thought I would let you all know that I am working on my 2nd wxPython book,
"Creating GUI Applications with wxPython". This one will be about actually
creating small runnable applications instead of just recipes like my Cookbook did. I hope
to have 8-10 working applications included with the book.

You can read more about it here if you are interested:
https://www.blog.pythonlibrary.org/2019/01/14/creating-gui-applications-with-wxpython-kickstarter/

Feel free to ask me questions about it too.

Thanks,
Mike

Mike,

Anyway, here is what I am looking for - hopefully it helps guide you.

* Performance is very good. Users hate to wait - for anything!

* GUI must support all desktops with a native look and feel. Kivy fails
this one. Will have mobile apps later in the year, so it would be nice
if one GUI fits all, but am ok with 2 gui's if needed.

* A great book taking me from beginner to expert.

Dave,

--
https://mail.python.org/mailman/listinfo/python-list

preferences file

2019-01-24 Thread Dave

I'm doing a small application and want to add user preferences.  Did 
some googling to see if there are standard Python ways/tools, but it 
seems not so much.  My specific questions are:


1. Best practices for a user preference file/system?

2. File format favored and why - ini, JSON, etc?

3. File location?  I'm using Ubuntu and I believe that the correct 
location would be home/.config/ .  What about Mac and Windows?


Would like to find a Python library that handles all of this, but so far...

Thanks,
Dave
--
https://mail.python.org/mailman/listinfo/python-list

System printer object

2019-01-07 Thread Dave

I need to print to one or both of my system printers.  I have not found 
a printer object in Python or in Tkinter.  This needs to work with 
Linux, Window, and Mac.  Can someone point me in the right direction? 
Ultimately, I want to have a File/Print in the menu that lets me select 
the printer and properties.


Thanks,
Dave
--
https://mail.python.org/mailman/listinfo/python-list

Re: Kivy native GUI examples

2019-01-07 Thread Dave


On 1/7/19 11:14 AM, Thomas Jollans wrote:

On 07/01/2019 15.51, Dave wrote:

I need to select a Python GUI.  It needs to cover all of the desktops
(Linux, Windows, Apple) and hopefully mobile (Android and Ios).  I'm
looking at Kivy, but have yet to find an example app. that has a native
looking GUI (Windows, Mac, Linux/Gnome/KDE).  Is that possible and
anyone know of some examples?


AFAIK looking like a native app is quite simply not something Kivy helps
you with. If that's important, you should look into other options such
as Qt (PyQt5 or PySide2).


-- Thomas



Thanks Thomas.
--
https://mail.python.org/mailman/listinfo/python-list

Kivy native GUI examples

2019-01-07 Thread Dave

I need to select a Python GUI.  It needs to cover all of the desktops 
(Linux, Windows, Apple) and hopefully mobile (Android and Ios).  I'm 
looking at Kivy, but have yet to find an example app. that has a native 
looking GUI (Windows, Mac, Linux/Gnome/KDE).  Is that possible and 
anyone know of some examples?


Thanks,
Dave
--
https://mail.python.org/mailman/listinfo/python-list

Re: Appending data to a json file

2017-04-04 Thread Dave


On 04/04/2017 01:50 PM, Rob Gaddi wrote:

On 04/04/2017 10:23 AM, Dave wrote:



I don't care for the idea of replacing the data file for every save. My
preference would to append to the existing data file - makes more sense.
However, that is not how json works.  So, I'm considering other
alternatives for a data file structure.  Paired data (key and value) is
not really required, but my feeling is that it makes the data file more
robust.  A database seems a little over the top for this situation since
there is no querying of data - just load and save.

Dave,


Valid.  That said, the database implementation (especially if you just
use Sqlite) is written, done, and works.  There are reasons that a lot
of programs use it just to store things like user settings.  Having a
backend that's already ACID takes a lot of stress out of things like
what I'm assuming you don't like about full data file replacement: what
happens if you get a powerfail midway through.

I'm not saying it's the right answer, but it's not nearly so much
flyswatting with a sledgehammer as you may think.



I'll take a look at it.  Thanks!

Dave,
--
https://mail.python.org/mailman/listinfo/python-list

Re: Appending data to a json file

2017-04-04 Thread Dave


On 04/04/2017 10:17 AM, Michael Torrie wrote:

On 04/03/2017 11:31 PM, dieter wrote:

Dave  writes:


I created a python program that gets data from a user, stores the data
as a dictionary in a list of dictionaries.  When the program quits, it
saves the data file.  My desire is to append the new data to the
existing data file as is done with purely text files.


Usually, you cannot do that:
"JSON" stands for "JavaScript Object Notation":


That's assuming he's using JSON; he never specified what he's using to
represent data as plain text.  Though I suspect you're correct, for all
we know he could just be writing data using his own text representation
or writing to an ini file.  And in his case it sounds like JSON is not
an ideal method for saving his data since he's wanting to only append
data, not read it in his program.

In the future, Dave, please provide all the information pertaining to
the problem so we can give accurate advice. Don't make us guess or
assume we can all infer this information.

I did.  Please see the subject - it is json, not some bastardized 
version of it.  While I didn't explicitly say that the data is read back 
in, it is - when the program starts.  The user can enter more data, then 
save the data to the list (append).  Then, like any other program, they 
can save the data to file.


I don't care for the idea of replacing the data file for every save. My 
preference would to append to the existing data file - makes more sense. 
However, that is not how json works.  So, I'm considering other 
alternatives for a data file structure.  Paired data (key and value) is 
not really required, but my feeling is that it makes the data file more 
robust.  A database seems a little over the top for this situation since 
there is no querying of data - just load and save.


Dave,
--
https://mail.python.org/mailman/listinfo/python-list

Appending data to a json file

2017-04-03 Thread Dave

I created a python program that gets data from a user, stores the data 
as a dictionary in a list of dictionaries.  When the program quits, it 
saves the data file.  My desire is to append the new data to the 
existing data file as is done with purely text files.  However, I can't 
find a way to do that.  The advice I have seen on the web is to load the 
data when the program starts, append the new user input to the list, 
then re-write the data file.  Is that the best way, or is there a better 
way?


Thanks,
Dave
--
https://mail.python.org/mailman/listinfo/python-list

where is it

2016-08-06 Thread Dave via Python-list

I am trying to associate the .py file extension with idle...where IS idle?  
Can you make it a bit more difficult to load/use your software please.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: exit from Tkinter mainloop Python 2.7

2016-02-24 Thread Dave Farrance

kevind0...@gmail.com wrote:

>from Tkinter import *
>
>def butContinue():
>root1.destroy()

As Christian said, you're destroying the root window and its children,
so instead use root1.quit() here.

> ...
>
>root1.mainloop()
>
>print entryName.get("1.0", "end-1c" )
>print entryPWord.get("1.0", "end-1c" )

And your root1.destroy() goes here instead. (The root window would
normally be destroyed on the script exit, but some IDE debuggers will
leave it open.) 
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: [newbie] Problem with matplotlib

2016-02-20 Thread Dave Farrance

Dave Farrance  wrote:

>It occurs to me now that the trackback might misidentify the module in
>use, if say, you'd named a file "numbers.py" then got rid of it later
>leaving a "numbers.pyc" somewhere. If so, see where it is:
>
>import numbers
>print numbers.__file__

I seem to have "numbers" on the brain. Replace with "decimal", of
course.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: [newbie] Problem with matplotlib

2016-02-20 Thread Dave Farrance

It occurs to me now that the trackback might misidentify the module in
use, if say, you'd named a file "numbers.py" then got rid of it later
leaving a "numbers.pyc" somewhere. If so, see where it is:

import numbers
print numbers.__file__
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: [newbie] Problem with matplotlib

2016-02-20 Thread Dave Farrance

jenswaelk...@gmail.com wrote:

>  File "/usr/lib/python2.7/decimal.py", line 3744, in 
>_numbers.Number.register(Decimal)
>AttributeError: 'module' object has no attribute 'Number'

Your decimal module seems broken. Confirm that in the Python shell:

import numbers
print numbers.Number

I'm guessing you'll get:
AttributeError: 'module' object has no attribute 'Number'

It appears to be the usual decimal module of the current linux system
python 2.7, so a corrupt hard disk?
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Tkinter problem: TclError> couldn't connect to display ":0

2016-02-05 Thread Dave Farrance

gemjack...@gmail.com wrote:

>This fixed my problem with thkinter.   sudo cp ~/.Xauthority ~root/

Which means that you were creating a GUI window with Python as root,
which is to be avoided if you can. If you can't avoid it and you're
running it with sudo in a bash console, rather than a root console, then
I'd suggest adding the line...

XAUTHORITY=$HOME/.Xauthority

...to the root's .bashrc which avoids putting a specific user's
xauthority file in the root directory.
-- 
https://mail.python.org/mailman/listinfo/python-list

Please Unsubscribe

2016-01-24 Thread Dave Tan


-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Install Numba on Debian

2016-01-23 Thread Dave Farrance

Dave Farrance  wrote:

>I'd like to install Numba on Debian Jessie to work with the system
>Python 2.7.9 (rather than installing Anaconda).

OK, never mind. Fixed.

By Googling the first error code, finding a suggested fix for that,
running again, Googling the new error, and several repeats of that, and
I've now got a working solution.

This recipe that somebody put on Github overcomes the main hurdle:
https://gist.github.com/sshillo/62955e46cb05e2b47ad3

The main issue seems to be that contrary to the instructions on the
Numba website, it's now a requirement to have  LLVM 3.6 installed, not
LLVM 3.5 which is in the Debian repository, and not LLVM 3.7 which is
the latest release at llvm.org.  Fortunately, a prebuilt LLVM 3.6 is
available at llvm.org.

Also I needed to install this lot from the Debian repository:

python-pip python-setuptools build-essential
python-enum34 libedit-dev python-dev
-- 
https://mail.python.org/mailman/listinfo/python-list

Install Numba on Debian

2016-01-23 Thread Dave Farrance

I'd like to install Numba on Debian Jessie to work with the system
Python 2.7.9 (rather than installing Anaconda).

When I follow the instructions at
https://github.com/numba/numba#custom-python-environments

...I get errors when trying to install Numba either with the git clone
method or installing it with pip.

I'll put the error log on Pastebin since its so large:
http://pastebin.com/gbrj0iHw

I've Googled for recipes for installing numba on Debian, installed every
Debian package suggested as a possible dependency, and still no luck.

Anybody know a working method for installing Numba on Debian Jessie
without Anaconda?
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: help

2016-01-15 Thread Dave Farrance

sam Rogers  wrote:

>  I have downloaded python 2.7  with no problem. It works. I am trying to get 
>pyserial to work. I have tried many different solutions. I am not  sure if it 
>works or not. How can I be sure? I am using windows 7.  I did not see any help 
>at python.org. Can you help?
>PS my goal is make this adafruit project work.
>https://learn.adafruit.com/arduino-lesson-17-email-sending-movement-detector/overview

Before using Python, have you verified that the IDE talks on the serial
port OK -- and that you can upload the simple blink sketch from its
provided examples and that you can change the blink rate of the LED?

Having done that, can you establish 2 way communication with Python?
What happens if you try the simple test script below? You will need to
change the "dev" line to whichever port you're using.


// Arduino sketch to echo serial port strings
char buf[81]; // max 80 chars + null
int siz = 0;  // size of input string
void setup(){
   Serial.begin(9600);
   Serial.setTimeout(100);
}
void loop(){
  siz = Serial.readBytesUntil('\n',buf,80); // get input string
  if (siz == 0) return;  // if timeout, loop again
  Serial.print("I heard: "); // reply with some text and
  buf[siz] = 0;  // must add null terminator
  Serial.println(buf);   // return original string
}


#!/usr/bin/env python2
import serial,time
# LINUX PORT -- change to "COM1" or whatever for Windows
dev = "/dev/ttyACM0"
ser = serial.Serial(dev, 9600, timeout=1)
time.sleep(2)   # Arduino starts in ~1.6s
while True:
  mystr = raw_input("Enter text max 80 chars: ")
  if mystr == '': break # terminate prog with 
  ser.flushInput()  # flush input just in case
  ser.write(mystr + '\n')   # send newline-terminated string
  txt = ser.readline(80)# read newline-terminated string
  print len(txt),"chars: ",txt, # \r\n included so add final comma
ser.close() # close port
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Turtle

2016-01-15 Thread Dave Farrance

Stallone Carl  wrote:

>I am currently using python 3.5.0 and I have been trying to write a program
>using turtle but is not seem to be working. I have followed all tutarial on
>the web and when i compare it with my code my am duing everything the same
>way but it still don't seems to be working I tryed repairen python but
>still no difference. Please help me.

OK.  Which tutorial?  What did you try?  What went wrong?  Was there an
error message?  If there was, what was it?

When learning something on a computer, start with the simplest possible
example.  Only when that's working do you move on to more complex stuff.
So with turtle graphics, start by writing a program that draws just one
line.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Unicode failure (Solved)

2015-12-06 Thread Dave Farrance

"D'Arcy J.M. Cain"  wrote:

>On Fri, 4 Dec 2015 18:28:22 -0500
>Terry Reedy  wrote:
>> Tk widgets, and hence IDLE windows, will print any character from
>> \u to \u without raising, even if the result is blank or ?.
>> Higher codepoints fail, but allowing the entire BMP is better than
>> any Windows codepage.
>
>Thanks to all.  Following up on the various posts brought me to
>information that solved my problem.  Basicall I added "export
>PYTHONIOENCODING=utf8" to my environment and "SetEnv PYTHONIOENCODING
>utf8" in my Apache config and now things are working as they should.
>
>Thanks all.

Hmmm. I hadn't seen this post before replying to the original because my
newsreader put this post in a later thread because:

(a) The subject header was changed
(b) The reference header is for a post that's not present in Usenet

That raises another question.  I'm seeing a number of broken threads
because people reply to posts that are not present in Usenet.  It's not
just my main news-server because my newreader can gather posts from
several Usenet servers and those posts are nowhere on Usenet.

Case in point:  The post by Terry Reedy quoted above, reference
. I presume that it's on the list server
even though it's not on Usenet.  Anybody know what's going on?
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Unicode failure

2015-12-06 Thread Dave Farrance

I was taking it for granted that you knew how to set environment
variables, but just in case you don't: In the shell, (are you using
BASH?), put this:

export PYTHONIOENCODING=UTF-8

...then run your script.

Remember that this is *not* a permanent fix.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Unicode failure

2015-12-06 Thread Dave Farrance

"D'Arcy J.M. Cain"  wrote:

>...
>utf-8
>Traceback (most recent call last):
>  File "./g", line 5, in 
>print(u"\N{TRADE MARK SIGN}")
>UnicodeEncodeError: 'ascii' codec can't encode character '\u2122' in
>position 0: ordinal not in range(128)

I *presume* that you're using Linux since you've got a hashbang, so...

You can *check* that it's the local environment that's the issue with
the *test* of setting the PYTHONIOENCODING environment variable. But if
that works, then it tells you must then fix the underlying environment's
character encoding to give a permanent fix.

$ PYTHONIOENCODING=UTF-8 python3 -c 'print(u"\u00A9")'
©

$ PYTHONIOENCODING=ascii python3 -c 'print(u"\u00A9")'
Traceback (most recent call last):
  File "", line 1, in 
UnicodeEncodeError: 'ascii' codec can't encode character '\xa9' in
position 0: ordinal not in range(128)
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Object identity has no necessary connection to memory location (was: What is a function parameter =[] for?)

Ben Finney  wrote:

>Dave Farrance  writes:
>
>> Marko Rauhamaa  wrote:
>>
>> >Dave Farrance :
>> >
>> >> (Conversely, I see that unlike CPython, all PyPy's numbers have
>> >> unchanging ids, even after exiting PyPy and restarting, so it seems
>> >> that PyPy's numerical ids are "faked".)
>> >
>> >What's a faked id?
>>
>> You can figure out what I'm getting at -- i.e. I presume that the ids
>> are not pointers to stored numbers in memory (as with CPython) but are
>> a translation of the numerical variable's value.
>
>Why refer to that as “faked”? That's what I can't figure out about what
>you're getting at. Perhaps Marko shares my uncomprehension.

Hence

https://en.wikipedia.org/wiki/Scare_quotes
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: What is a function parameter =[] for?

Marko Rauhamaa  wrote:

>Dave Farrance :
>
>> (Conversely, I see that unlike CPython, all PyPy's numbers have
>> unchanging ids, even after exiting PyPy and restarting, so it seems
>> that PyPy's numerical ids are "faked".)
>
>What's a faked id?

You can figure out what I'm getting at -- i.e. I presume that the ids
are not pointers to stored numbers in memory (as with CPython) but are a
translation of the numerical variable's value.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Help needed with compiling python

Cecil Westerhof  wrote:

>On Wednesday 25 Nov 2015 23:58 CET, Laura Creighton wrote:
>>
>> Your Suse system probably wants to use python for something. If your
>> system python is damaged, you badly need to fix that, using the
>> system package managers tools, before Suse does some sort of update
>> on you, using the broken python, which damages more of your system.
>
>I tried that. But it installs only things in /usr/lib and /usr/lib64,
>nothing in /usr/bin, but at the same time it is adamant that it
>installed python. I wanted a quick fix, but it looks like that is not
>going to work. :'-( I'll have to find a way to get things fixed.

A complete reinstall of Suse (after saving your home directory and work)
might be quickest if you're in the dark about what's broken.

But you might be able to fix it.  If you can figure out which packages
contain the damaged files, then do forced reinstalls of those.  I've not
used Suse, but a quick Google tells me that the syntax is:

zypper in -f 

So you'll want to try package names like "python" and "python2.7".
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: What is a function parameter =[] for?

Alan Bawden  wrote:

>Chris Angelico  writes:
> ...
>> Python 2.7.8 (2.4.0+dfsg-3, Dec 20 2014, 13:30:46)
>> [PyPy 2.4.0 with GCC 4.9.2] on linux2
>> Type "help", "copyright", "credits" or "license" for more information.
>> tuple([]) is tuple([])
>> False
>
>I said I wouldn't be suprised if it was always true, but that doesn't
>imply that I need to be suprised if it is sometimes false!
>
>Having said that, I _am_ curious whether that remains False for various
>other variant expressions.  "tuple([])" is actually a rather perverse
>way to obtain an empty tuple.  How about plain "() is ()"? ...

Still false in PyPy it seems

[PyPy 2.6.1 with GCC 4.9.2] on linux2
 id(())
139836165383760L
 id(())
139836165383776L

(Conversely, I see that unlike CPython, all PyPy's numbers have
unchanging ids, even after exiting PyPy and restarting, so it seems that
PyPy's numerical ids are "faked".)

[PyPy 2.6.1 with GCC 4.9.2] on linux2
 id(1+2j)
679900119843984469027190799480815353863L

[PyPy 2.6.1 with GCC 4.9.2] on linux2
 id(1+2j)
679900119843984469027190799480815353863L
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Is there any reason to introduce this intermediate variable (sz)?

2015-11-18 Thread Dave Farrance

fl  wrote:

>Hi,
>I find the following code snippet, which is useful in my project:
> ...
>correctly. Could you see something useful with variable 'sz'?

So that's example code in "An Introduction to the Kalman Filter" by Greg
Welch and Gary Bishop, and no, that construct was unnecessary. As you've
figured out, you can use the integer directly.

It's the usual problem that people get when they switch from using
Octave/Matlab to numpy/scipy/matplotlib. The former are better in an
interactive maths-oriented environment, but people then often then
switch to Python for more complex algorithms to take advantage of the
features of an advanced general-purpose programming language. The
problem that people then run into is that although there are equivalents
in the Python libraries for most of the Matlab functions, this happens
to be an area where the documentation is particularly uneven.

"Pylab" is a project that attempted to be a Python equivalent of Matlab,
but has now become a depreciated appendix to matplotlib. There have been
attempts to restart it as a feature of Ipython, but although it mostly
works, the documentation is almost nonexistent. The only way to figure
out what it can do is to try it yourself with a lot of trial and error.

Anyway, don't be surprised if you see unnecessary elaborations in
maths/science Python code because it's what you expect when people are
arriving at code that works from reading poor documentation, trial and
error, and Googling other peoples code snippets. Just try it yourself
and save yourself time rather than asking for hand-holding.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Problems using struct pack/unpack in files, and reading them.

2015-11-17 Thread Dave Farrance

Steven D'Aprano  wrote:

>On Mon, 16 Nov 2015 05:15 pm, Gregory Ewing wrote:
>
>> Ints are not the only thing that // can be applied to:
>> 
>>  >>> 1.0//0.01
>> 99.0
>
>Good catch!

Hmmm. I see that the float for 0.01 _is_ slightly larger than 0.01

>>> Decimal(0.01)
Decimal('0.0120816681711721685132943093776702880859375')

But it seems that 1.0 // 0.01 is not directly equivalent to:

>>> int(1.0 / 0.01)
100

And I see that:

>>> Decimal(1.0 / 0.01)
Decimal('100')
>>> floor(1.0 / 0.01)
100
>>> 0.01 * 100.0 - 1.0
0.0

So I guess that the // operator is _very_ strict in its "floor division"
of floats, but that the "/" operator returns the nearest float value.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: What is '@' for

2015-11-14 Thread Dave Farrance

fl  wrote:

>I read the following code snippet. A question is here about '@'.
>I don't find the answer online yet.

I recommend this:

"Understanding Python Decorators in 12 Easy Steps!"

http://simeonfranklin.com/blog/2012/jul/1/python-decorators-in-12-steps/
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: don't understand matrix-multiplication should be reversed in python?

2015-11-13 Thread Dave Farrance

PythonDude  wrote:

>On Thursday, 12 November 2015 22:57:21 UTC+1, Robert Kern  wrote:

>> He simply instantiated the two vectors as row-vectors instead of 
>> column-vectors, 
>> which he could have easily done, so he had to flip the matrix expression.
>
>Thank you very much Robert - I just had to be sure about it :-)

Yep, he's evidently used to the Matlab/Octave way of defining "vectors"
which is somewhat easier for a math-oriented interactive environment.

It's just a *bit* more laborious to append columns in numpy.

>>> from numpy import *
>>> v1=vstack([0,1,2])
>>> v2=vstack([3,4,5])
>>> c_[v1,v2]
array([[0, 3],
   [1, 4],
   [2, 5]])
>>> append(v1,v2,axis=1)
array([[0, 3],
   [1, 4],
   [2, 5]])
>>> v3=mat('4;5;6')
>>> v4=mat('7;8;9')
>>> c_[v3,v4]
matrix([[4, 7],
[5, 8],
[6, 9]])
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Unbuffered stderr in Python 3

2015-11-04 Thread Dave Farrance

Random832  wrote:

>The opposite of line buffering is not no buffering, but full
>(i.e. block) buffering, that doesn't get flushed until it runs
>out of space. TextIOWrapper has its own internal buffer, and its
>design apparently doesn't contemplate the possibility of using
>it with a raw FileIO object (which may mean that the posted code
>isn't guaranteed to work) or disabling buffering.

Hmmm. That even seems to cause trouble for sys.stderr.write
(in Python3 with a non-tty e.g. a piped output):

$ python2 -c 'import sys;sys.stderr.write("1\n");print("2")' 2>&1 | tee
1
2
$ python3 -c 'import sys;sys.stderr.write("1\n");print("2")' 2>&1 | tee
2
1
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: python doesn't install

2015-11-02 Thread Dave Farrance

Tim Golden  wrote:

>I'm afraid you've been bitten by the fact that we no longer support 
>Windows XP and haven't communicated this very well. We have a new 
>version of the installer almost ready for release which indicates this 
>much earlier (and more obviously). I'm afraid if you're on XP you're 
>limited to Python 3.4 and earlier, all of which are perfectly usable I'm 
>happy to say!

I've been reading the comments about Python and XP on this group -- and
I must say that I'm thinking: Doesn't pretty much every other Windows
software package tell you the minimum requirements -- because that's the
first thing you'd want to know?

So I've Googled for "python 3.5 minimum requirements":

1st hit: "Using Python on Windows -- Python 3.5.0 documentation"
and a few paragraphs down that page there's:
"Python on XP --  7 Minutes to Hello World by Richard Dooling, 2006"
which says how easy it is to install on XP.

2nd hit: "Download Python -- Python.org"
There's download links but nothing about XP, but there's a link for
"Information about specific ports" -- so click on "Windows"
and no information actually, just more download links.

3rd hit: "Welcome to Python.org"
There's download links and no info about minimum requirements.

And so on down the page of Google hits.

Yes, I've read the justifications. Why list all the non-supported OSs?
And the explanation about each version of Python being supported just
for the supported versions of Windows upon its release is in the
documentation -- somewhere.  But it still seems to me that stating the
minimum requirements in a place that people would tend to look for it is
a... minimum requirement.

If the developers really are determined not to mention specific versions
of Windows (If it was me, I'd have probably mentioned that the most
recent version required Vista somewhere on the download page), then
maybe adding the comment about matching the release date of Python to
the supported versions of Windows to the download pages would give
people some sort of clue as to what's going on.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: Pyserial and Ubuntu Linux kernel 3.13.0-65-generic

2015-10-07 Thread Dave Farrance

Rob Gaddi  wrote:

>So, this is odd.  I'm running Ubuntu 14.04, and my system did a kernel 
>upgrade from the repository from 3.13.0-63-generic to 3.13.0-65-generic.  
>And pyserial (2.7, installed through pip) stopped working.

When KDE's "Plasma 5" appeared with Kubuntu 15.04, I found it to be too
new and have too many dysfunctions, so I reverted to Kubuntu 14.04 LTS.

Now this problem.  Looking at the Ubuntu 14.04 repository, I found that
it contained a backported version of the kernel used in 15.04.  So...

Remove "meta" packages that have latest 3.13 kernel as dependencies:

sudo apt-get purge linux-generic linux-signed-generic

Install meta packages that pull in the latest 3.19 kernel:

sudo apt-get install linux-generic-lts-vivid
  linux-signed-generic-lts-vivid

Serial now works fine. The later kernel introduces no functional changes
in (K)ubuntu 14.04 that I can discern.  I presume that since it is a
"backported" version of the 3.19 kernel, that its video drivers have
been matched to Ubuntu 14.04's version of X.Org, and so on.

Anyway, that's what works for me. I could've put a "hold" on the
3.13.0-63 kernel, but this seems a better fix.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: matplotlib timer

Laura Creighton  wrote:

>In a message of Thu, 01 Oct 2015 20:03:26 +0100, Dave Farrance writes:
>>Laura Creighton  wrote:
>>
>>>In a message of Thu, 01 Oct 2015 18:45:06 +0100, Dave Farrance writes:
>>>>Yet the documentation says that it's mandatory for the GUI backend base
>>>>to implement stop() but that single_shot is optional. Ho hum.
>>>
>>>report as a bug.  its a doc bug at least, but I think its a real bug,
>>>and your code should have worked.
>>>
>>>https://github.com/matplotlib/matplotlib/issues
>>
>>OK, done.
>>
>
>Thank you.
>
>Can you add how you got it to work, and the doc you read
>that seems wrong?

OK.
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: matplotlib timer

Laura Creighton  wrote:

>In a message of Thu, 01 Oct 2015 18:45:06 +0100, Dave Farrance writes:
>>Yet the documentation says that it's mandatory for the GUI backend base
>>to implement stop() but that single_shot is optional. Ho hum.
>
>report as a bug.  its a doc bug at least, but I think its a real bug,
>and your code should have worked.
>
>https://github.com/matplotlib/matplotlib/issues

OK, done.

https://github.com/matplotlib/matplotlib/issues/5163
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: matplotlib timer

Laura Creighton  wrote:

>In a message of Thu, 01 Oct 2015 17:36:50 +0100, Dave Farrance writes:
>>I'm trying to set up the basics of a timer-scheduled function in
>>matplotlib and I can't figure out how to stop the timer. Maybe the
>>stop() method is dysfunctional in Ubuntu 14.04 or maybe I'm getting the
>>syntax wrong.
>>
>>If anybody's got matplotlib installed, can you try this code and tell me
>>if it stops after one tick as it should -- or does it continue printing
>>every second without stopping as mine does?
>>
>>#!/usr/bin/env python
>>import matplotlib.pyplot as P
>>def fn():
>>  timer.stop()
>>  print("tick")
>>fig, ax = P.subplots()
>>timer = fig.canvas.new_timer(interval=1000)
>>timer.add_callback(fn)
>>timer.start()
>>P.show()
>> 
>
>debian unstable
>Python 3.4.3+ (default, Jul 28 2015, 13:17:50)
>
>mine ticks forever, too.

Thanks. I've just figured out how to stop the timer.

replace "timer.stop()" with
timer.single_shot = True

Yet the documentation says that it's mandatory for the GUI backend base
to implement stop() but that single_shot is optional. Ho hum.

http://matplotlib.org/api/backend_bases_api.html#matplotlib.backend_bases.TimerBase
-- 
https://mail.python.org/mailman/listinfo/python-list

matplotlib timer