Re: [Tutor] Exception Handling
David da...@abbottdavid.com wrote Is this the correct way to handle a ValueError exception and should I get in the practice of catching them? Yes and Yes. Although I woulfd move the except clause up to just after the input section (which is where the errors will be raised). A couple of other comments below: while True: try: yr = int(raw_input(What year were you born? )) mn = int(raw_input(What month were you born? )) dy = int(raw_input(What day were you born? )) curr_date = time.strftime(%Y %m %d, time.gmtime()) ynum = int(time.strftime(%Y, time.gmtime())) - int(yr) mnum = int(time.strftime(%m, time.gmtime())) dnum = int(time.strftime(%d, time.gmtime())) mn = int(mn) dy = int(dy) Put the except here, its easier to see where the error came from. And since the error message only applies to these int() calls its more accurate. if mn - mnum: print You are %i % ynum, years old. This is an odd use of string formatting, more usually you would only use one string: print You are %i years old % ynum Either that or just insert the value and not use formattting: print You are, ynum, years old. else: ret = int(ynum) - 1 You don't need the int conversion here since yuou already did it at the input stage. But... print You are %i % ret, years old. Why not just print You are %i % ynum-1, years old. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Exception Handling
bob gailer bgai...@gmail.com wrote Also IMHO it is bad design to put a lot of code inside a try block. In this case the user might make a mistake on day and then is forced to reenter the year and month! Obviously there is no absolute rule here but I disagree. One of the biggest advantages of try/except error handling is that it keeps the mess of handling errors out of the main logic of the code. This has two effects: 1) Code that is much easier to read 2) a lot less error handling code Using big bite try/except does mean the except clauses become more complex if you want to find out exactly which line caused the error, as in the example above, but it can be done by examining the traceback, but in general I much prefer to wrap logical blocks of code using try/except rather than only one or two lines Better to write a function for requesting an integer from the user which loops until the user gets it right (with some way to escape if he gets frustrated and just wants to quit. And this I agree with. If you do want to check each line use a function that incorporates the checking within it and call that to get a guaranteed result. And that keeps both Bob and I happy with the try/excepts stylistically speaking :-) -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Printing the code of a function
wormwood_3 wormwoo...@yahoo.com wrote I am wondering if there is a way to print out the code of a defined function. Its not reliable but I think you can use func.func_code.filename func.func_code.firstlineno To find the first line of code in the original source file. Its up to you to figure out the last line though! I guess checking for the next line with equivalent indentation might work. But I'm not sure how much good it would do you... unless you were writing a debugger maybe? Alan G ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] optional parameter in list comprehension
hello!I am a novice looking up to the tutor as my Guide.
I got a problem while using optional parameter.
#! user/bin/env python
import os
def myfiles(directory,extension=None):
for x in [os.path.join(x,i) for x,y,z in os.walk(directory)\
for i in z if i.endswith(extension)]:print x
if __name__=='__main__':
import sys
myfiles(sys.argv[1],sys.argv[2])
myfiles.myfiles('C:\\python26')
Traceback (most recent call last):
File pyshell#17, line 1, in module
myfiles.myfiles('C:\\python26')
File C:\Python26\lib\site-packages\myfiles.py, line 6, in myfiles
for i in z if i.endswith(extension)]:print x
TypeError: expected a character buffer object
myfiles.myfiles('C:\\python26','doc')
C:\python26\Doc\examples.doc
How can I rectify this?
Thanks
Prasad
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Re: [Tutor] optional parameter in list comprehension
def myfiles(directory,extension=None): for x in [os.path.join(x,i) for x,y,z in os.walk(directory)\ if extension: for i in z if i.endswith(extension)]:print x Dj Gilcrease OpenRPG Developer ~~http://www.openrpg.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] optional parameter in list comprehension
Dj Gilcrease wrote: def myfiles(directory,extension=None): for x in [os.path.join(x,i) for x,y,z in os.walk(directory)\ if extension: SYNTAX ERROR! for i in z if i.endswith(extension)]:print x -- Bob Gailer Chapel Hill NC 919-636-4239 ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] optional parameter in list comprehension
prasad rao wrote:
hello!
I am a novice looking up to the tutor as my Guide.
I got a problem while using optional parameter.
#! user/bin/env python
import os
def myfiles(directory,extension=None):
change that to def myfiles(directory,extension=):
for x in [os.path.join(x,i) for x,y,z in os.walk(directory)\
for i in z if i.endswith(extension)]:print x
if __name__=='__main__':
import sys
myfiles(sys.argv[1],sys.argv[2])
myfiles.myfiles('C:\\python26')
Traceback (most recent call last):
File pyshell#17, line 1, in module
myfiles.myfiles('C:\\python26')
File C:\Python26\lib\site-packages\myfiles.py, line 6, in myfiles
for i in z if i.endswith(extension)]:print x
TypeError: expected a character buffer object
myfiles.myfiles('C:\\python26','doc')
C:\python26\Doc\examples.doc
How can I rectify this?
Thanks
Prasad
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--
Bob Gailer
Chapel Hill NC
919-636-4239
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Re: [Tutor] Exception Handling
On Mon, 29 Dec 2008 09:10:45 - Alan Gauld alan.ga...@btinternet.com wrote: bob gailer bgai...@gmail.com wrote Also IMHO it is bad design to put a lot of code inside a try block. In this case the user might make a mistake on day and then is forced to reenter the year and month! Obviously there is no absolute rule here but I disagree. One of the biggest advantages of try/except error handling is that it keeps the mess of handling errors out of the main logic of the code. This has two effects: 1) Code that is much easier to read 2) a lot less error handling code Using big bite try/except does mean the except clauses become more complex if you want to find out exactly which line caused the error, as in the example above, but it can be done by examining the traceback, but in general I much prefer to wrap logical blocks of code using try/except rather than only one or two lines I often use the else clause of try...except. This allows putting only the minimum problematic code lines inside the try block, which is good both for legibility andto avoid catching unexpected errors. The else will be executed only in case of no exception: try: problematic_instructions except ExceptionType, exception: expected_exception_handler else: further_standard_process denis -- la vida e estranya ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Printing the code of a function
On Mon, 29 Dec 2008 09:18:43 - Alan Gauld alan.ga...@btinternet.com wrote: wormwood_3 wormwoo...@yahoo.com wrote I am wondering if there is a way to print out the code of a defined function. Its not reliable but I think you can use func.func_code.filename func.func_code.firstlineno To find the first line of code in the original source file. Its up to you to figure out the last line though! I guess checking for the next line with equivalent indentation might work. But I'm not sure how much good it would do you... unless you were writing a debugger maybe? Alan G I would do it so by parsing source file: * (convert indents to tabs (easier to parse)) * search for a line that start with (n indents) + def func_name * record all following lines that start with (n+1 indents) or more * stop where a line starts with (n indents) or less denis -- la vida e estranya ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Printing the code of a function
On Sun, Dec 28, 2008 at 8:49 PM, wormwood_3 wormwoo...@yahoo.com wrote: Hello all, This might be trivially easy, but I was having a hard time searching on it since all the component terms are overloaded:-) I am wondering if there is a way to print out the code of a defined function. If the source code is available try inspect.getsource(). Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Modifying a QIF
Hello, this weekend I had fun using Python for text processing. I
needed to change a qif converted from a ofx, using the tool MT2OFX
(http://www.xs4all.nl/~csmale/mt2ofx/en/index.htm)
I wanted to change transactions like these:
D11/14/2008
MCHEQUE 102 17590807;Cheque or Preauth. Debit
T-500.00
N102
^
Into this:
D11/14/2008
MCHEQUE 102 17590807;Cheque or Preauth. Debit
T-500.00
N102
PLorne Koehn
LHousing:Rent
== That is, insert those given Payee and Category if the transaction
was a cheque of 500.00
I came up with these two versions and would like to know which should
be more efficient or practical. Could you point improvements?
VERSION ONE:
f = open('cibc.QIF', 'r').readlines()
for line in range(len(f)):
if f[line] == 'T-500.00\n':
f[line+1] += 'PLorne Koehn\nLHousing:Rent\n'
new = open('cibc.QIF', 'w')
new.writelines(f)
VERSION TWO:
f = open('cibc.QIF', 'rw')
g = open('newresult.qif', 'w')
flag = 0
for line in f:
if line == 'T-500.00\n':
flag = 1
elif line.startswith('N') and flag:
flag = 0
line += 'PLorne Koehn\nLHousing:Rent\n'
g.write(line)
f.close()
#==
One thing like about version 1 is that I can overwrite the same
file, and don't need to create another one. I haven't figured out how
to do the same with the second version and overcoming the IOError.
Thanks for your attention
Edu
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Re: [Tutor] Modifying a QIF
On Mon, 29 Dec 2008 13:18:55 -0700
Eduardo Vieira eduardo.su...@gmail.com wrote:
Hello, this weekend I had fun using Python for text processing. I
needed to change a qif converted from a ofx, using the tool MT2OFX
(http://www.xs4all.nl/~csmale/mt2ofx/en/index.htm)
I wanted to change transactions like these:
D11/14/2008
MCHEQUE 102 17590807;Cheque or Preauth. Debit
T-500.00
N102
^
Into this:
D11/14/2008
MCHEQUE 102 17590807;Cheque or Preauth. Debit
T-500.00
N102
PLorne Koehn
LHousing:Rent
== That is, insert those given Payee and Category if the transaction
was a cheque of 500.00
I came up with these two versions and would like to know which should
be more efficient or practical. Could you point improvements?
VERSION ONE:
f = open('cibc.QIF', 'r').readlines()
for line in range(len(f)):
if f[line] == 'T-500.00\n':
f[line+1] += 'PLorne Koehn\nLHousing:Rent\n'
new = open('cibc.QIF', 'w')
new.writelines(f)
I would change 'line' -- 'line_nr' or 'lineno'
or
for line,index in enumerate(f)
no!
for index,line in enumerate(f)
;-)
VERSION TWO:
f = open('cibc.QIF', 'rw')
g = open('newresult.qif', 'w')
flag = 0
for line in f:
if line == 'T-500.00\n':
flag = 1
elif line.startswith('N') and flag:
flag = 0
line += 'PLorne Koehn\nLHousing:Rent\n'
g.write(line)
f.close()
#==
One thing like about version 1 is that I can overwrite the same
file, and don't need to create another one. I haven't figured out how
to do the same with the second version and overcoming the IOError.
maybe by first writing on a string instead directly to a file -- then flush the
whole text to the same file:
text =# replaces g
...
text += line
...
f = open('cibc.QIF', 'w')
f.write(text)
Thanks for your attention
Edu
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--
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Re: [Tutor] Exception Handling
spir denis.s...@free.fr wrote I often use the else clause of try...except. This allows putting only the minimum problematic code lines inside the try block, which is good both for legibility andto avoid catching unexpected errors. The else will be executed only in case of no exception: try: problematic_instructions except ExceptionType, exception: expected_exception_handler else: further_standard_process Thats exactly what I try to avoid. The big win for me in try/except is that I can put the whole logic of a function together with no error code confusing the picture. The above is no better than the old BASIC style error handling problemInstruction if errorcode == XXX: handle error further instruction I find that much harder to follow the normal case code than: try: problematic instructions more instructions more problems except Error1 handleError1 except Error2: handleError2 Now I can see the real algorithm and the errors are all tiucked out of the way at the bottom where I don't need to read them until its necessary. Assuming you don't wrte functions that are hundreds of lines long that doesn't cause me any problerms when debugging but greatly increases the readability The only somewhat valid case for doing line by line exceptions is IMHO the one that started this - where users are entering input and would need to start right at the beginning in the event of an error. But as Bob pointed out you can avoid that by writing a convertion function to do the error handling and validation and call it repeatedly. But it is largely a matter of personal taste. Alan G. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
