[Tutor] Confused about globals
Hi
I have a series of python programs that plot stuff using PYX. Common to
these is the need to read in a list of (well) locations in (X,Y) coords so
I put that code in a separate module called shared_funcs.py. The coords
are stored in dictionaries which I want to use later in the main program
- every time I find a well with data, I can get the well's (x,y) coords by
looking up the well name in the dictionary. The code snippet looks like this:
=== main.py
# define coord dictionaries for global use
DE={}
DN={}
import shared_funcs()
shared_funcs.get_xy_data() # Get coords from file
... do plotting stuff
=== shared_funcs.py ===
def get_xy_data():
in_file=open(well_xy.txt,r)
for line in in_file
L=line.split()
well=L[0]
x=L[1]
y=L[2]
DE[well]=x
DN[well]=y
in_file.close()
The problem is that DE and DN appear not to be accessible to get_xy_data -
presumably this is because shared_funcs.py and main.py don't share the same
scope. So, is there any way to let get_xy_data change DE and DN? I guess
the obvious way is to pass them to get_xy_data as arguments - but is there
a more pythonic method? Thanks in advance!
___
Tutor maillist - Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Confused about globals
As a note, the import should be
import shared_funcs
In Python, most globals aren't really global -- they're local to the
module. If you split your modules by functionality, then variables
should naturally relate to a specific module, and be located there.
So, for example, you could move those global variables to
shared_funcs.py, renamed to wells.py:
=== wells.py ==
DE={}
DN={}
def get_xy_data():
in_file=open(well_xy.txt,r)
for line in in_file
L=line.split()
well=L[0]
x=L[1]
y=L[2]
DE[well]=x
DN[well]=y
in_file.close()
def lookup_well(well):
return (DE.get(well, None), DN.get(well, None))
=== main.py ===
import wells
def func_that_needs_wells():
...
for e n wells.DE.keys():
...
...
etc.
On Jun 9, 2006, at 4:42 AM, Etrade Griffiths wrote:
Hi
I have a series of python programs that plot stuff using PYX. Common
to
these is the need to read in a list of (well) locations in (X,Y)
coords so
I put that code in a separate module called shared_funcs.py. The
coords
are stored in dictionaries which I want to use later in the main
program
- every time I find a well with data, I can get the well's (x,y)
coords by
looking up the well name in the dictionary. The code snippet looks
like this:
=== main.py
# define coord dictionaries for global use
DE={}
DN={}
import shared_funcs()
shared_funcs.get_xy_data() # Get coords from file
... do plotting stuff
=== shared_funcs.py ===
def get_xy_data():
in_file=open(well_xy.txt,r)
for line in in_file
L=line.split()
well=L[0]
x=L[1]
y=L[2]
DE[well]=x
DN[well]=y
in_file.close()
The problem is that DE and DN appear not to be accessible to
get_xy_data -
presumably this is because shared_funcs.py and main.py don't share the
same
scope. So, is there any way to let get_xy_data change DE and DN? I
guess
the obvious way is to pass them to get_xy_data as arguments - but is
there
a more pythonic method? Thanks in advance!
___
Tutor maillist - Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
___
Tutor maillist - Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Confused about globals
Etrade Griffiths wrote:
Hi
I have a series of python programs that plot stuff using PYX. Common to
these is the need to read in a list of (well) locations in (X,Y) coords so
I put that code in a separate module called shared_funcs.py. The coords
are stored in dictionaries which I want to use later in the main program
- every time I find a well with data, I can get the well's (x,y) coords by
looking up the well name in the dictionary.
You don't need a global variable in shared_funcs.get_xy_data() at all.
It is reading a file and creating two dicts. I would write it to create
and return the dicts. Then you can save them where you like in the
caller. Also, I would use one dict whose values are (x, y) pairs, rather
than two parallel dicts. Then your code looks like this:
=== shared_funcs.py ===
def get_xy_data():
D = {}
in_file=open(well_xy.txt,r)
for line in in_file
L=line.split()
well=L[0]
x=L[1]
y=L[2]
D[well]=(x, y)
in_file.close()
return D
=== main.py ===
import shared_funcs
D = shared_funcs.get_xy_data()
though I suggest a more descriptive name than D...
If there are other related bits of data or operations other than lookup,
that might point to using a class to wrap the dict, the other data and
operations.
Kent
___
Tutor maillist - Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
