Re: How to pass a global variable to a module?
On Tuesday, 29 September 2009 20:24:53 Mars creature wrote: From the link Gregor posted, it seems no way to share variable between modules. I can understand the point that global variables tends to mess up programs. Assume that I have 10 parameters need to pass to the function. If these parameters are fixed, I can use another module to store these 10 parameters, and import to the module, as suggested by jean-michel. But what if these 10 parameters will be changed in the main program? Passing the variable to the function as a parameter suggested by Rami will certainly do, but I am wondering weather there are other ways. What you'd like to code it? You can put all the 10 things in a file called say my_params.py. Then where you need it, you do either: from my_params import * to make them available where needed, or: import my_params as p and access them as: print p.my_parm_1,p.my_parm_2,p.my_parm_3,p.my_parm_4 - Hendrik -- http://mail.python.org/mailman/listinfo/python-list
Re: How to pass a global variable to a module?
Mars creature wrote: On Sep 29, 12:49 pm, Rami Chowdhury rami.chowdh...@gmail.com wrote: On Tue, 29 Sep 2009 09:40:29 -0700, Mars creature jin...@gmail.com wrote: Dear Python users, I just start to use python and love this language. I met this problem when I try to save my functions in a separate file. The question is how I can pass a global variable to a function which is saved in another file. If I save the function I defined in the same file with the main program, there is no problem after I declare the global variable. But problem comes out when I save all the function is a separate file. Help is very much appreciated! Thanks! Jinbo In Python, as in many other languages, I'd advise that you think about whether your variable needs to be global, or whether you could (or should) simply pass the variable to the function as a parameter. HTH, Rami -- Rami Chowdhury Never attribute to malice that which can be attributed to stupidity -- Hanlon's Razor 408-597-7068 (US) / 07875-841-046 (UK) / 0189-245544 (BD) Thank you guys for the prompt and helpful response. From the link Gregor posted, it seems no way to share variable between modules. I can understand the point that global variables tends to mess up programs. Assume that I have 10 parameters need to pass to the function. If these parameters are fixed, I can use another module to store these 10 parameters, and import to the module, as suggested by jean-michel. But what if these 10 parameters will be changed in the main program? Passing the variable to the function as a parameter suggested by Rami will certainly do, but I am wondering weather there are other ways. What you'd like to code it? Thank you very much! Jinbo Why don't you post the function you're trying to code, with the parameter names ? Write the documentation for that function, write what it is supposed to do, the parameters, their purpose and the returned value. Just by doing this, you may be able to find all by yourself what should be the correct function prototype. JM -- http://mail.python.org/mailman/listinfo/python-list
Re: How to pass a global variable to a module?
On Sep 30, 5:31 am, Jean-Michel Pichavant jeanmic...@sequans.com wrote: Mars creature wrote: On Sep 29, 12:49 pm, Rami Chowdhury rami.chowdh...@gmail.com wrote: On Tue, 29 Sep 2009 09:40:29 -0700, Mars creature jin...@gmail.com wrote: Dear Python users, I just start to use python and love this language. I met this problem when I try to save my functions in a separate file. The question is how I can pass a global variable to a function which is saved in another file. If I save the function I defined in the same file with the main program, there is no problem after I declare the global variable. But problem comes out when I save all the function is a separate file. Help is very much appreciated! Thanks! Jinbo In Python, as in many other languages, I'd advise that you think about whether your variable needs to be global, or whether you could (or should) simply pass the variable to the function as a parameter. HTH, Rami -- Rami Chowdhury Never attribute to malice that which can be attributed to stupidity -- Hanlon's Razor 408-597-7068 (US) / 07875-841-046 (UK) / 0189-245544 (BD) Thank you guys for the prompt and helpful response. From the link Gregor posted, it seems no way to share variable between modules. I can understand the point that global variables tends to mess up programs. Assume that I have 10 parameters need to pass to the function. If these parameters are fixed, I can use another module to store these 10 parameters, and import to the module, as suggested by jean-michel. But what if these 10 parameters will be changed in the main program? Passing the variable to the function as a parameter suggested by Rami will certainly do, but I am wondering weather there are other ways. What you'd like to code it? Thank you very much! Jinbo Why don't you post the function you're trying to code, with the parameter names ? Write the documentation for that function, write what it is supposed to do, the parameters, their purpose and the returned value. Just by doing this, you may be able to find all by yourself what should be the correct function prototype. JM The function I am trying to code is quite simple and nothing special. I guess what I wanted to say was how to avoid typing all parameters everytime I am using the function. I used to use common block in Fortran to keep the frequently used data. I could've put all parameters in a file and import it, if they are unchangable. But in my case the parameters are changing. Allow me to say, unpacking the list or dictionary is the answer I wanted, although this is too trivial for some of you. Based on the discussion (correct me if I'm wrong), 1, try to avoid global, 2, if parameters are constant, put them in a tuple/list/dictionary and import them 3, if parameters are changeable, pack them into a list/dictionary and use *params (for list) or **params (for dict) to unpack and pass to the function. I want to thank you all! It's quite bit learning for me from your discussion. Jinbo -- http://mail.python.org/mailman/listinfo/python-list
Re: How to pass a global variable to a module?
Mars creature wrote: On Sep 30, 5:31 am, Jean-Michel Pichavant jeanmic...@sequans.com wrote: Mars creature wrote: On Sep 29, 12:49 pm, Rami Chowdhury rami.chowdh...@gmail.com wrote: On Tue, 29 Sep 2009 09:40:29 -0700, Mars creature jin...@gmail.com wrote: Dear Python users, I just start to use python and love this language. I met this problem when I try to save my functions in a separate file. The question is how I can pass a global variable to a function which is saved in another file. If I save the function I defined in the same file with the main program, there is no problem after I declare the global variable. But problem comes out when I save all the function is a separate file. Help is very much appreciated! Thanks! Jinbo In Python, as in many other languages, I'd advise that you think about whether your variable needs to be global, or whether you could (or should) simply pass the variable to the function as a parameter. HTH, Rami -- Rami Chowdhury Never attribute to malice that which can be attributed to stupidity -- Hanlon's Razor 408-597-7068 (US) / 07875-841-046 (UK) / 0189-245544 (BD) Thank you guys for the prompt and helpful response. From the link Gregor posted, it seems no way to share variable between modules. I can understand the point that global variables tends to mess up programs. Assume that I have 10 parameters need to pass to the function. If these parameters are fixed, I can use another module to store these 10 parameters, and import to the module, as suggested by jean-michel. But what if these 10 parameters will be changed in the main program? Passing the variable to the function as a parameter suggested by Rami will certainly do, but I am wondering weather there are other ways. What you'd like to code it? Thank you very much! Jinbo Why don't you post the function you're trying to code, with the parameter names ? Write the documentation for that function, write what it is supposed to do, the parameters, their purpose and the returned value. Just by doing this, you may be able to find all by yourself what should be the correct function prototype. JM The function I am trying to code is quite simple and nothing special. I guess what I wanted to say was how to avoid typing all parameters everytime I am using the function. I used to use common block in Fortran to keep the frequently used data. I could've put all parameters in a file and import it, if they are unchangable. But in my case the parameters are changing. Write a function that calls the function you want to call, taking the arguments you want to retype, and filling in all the arguments you don't: def stand_in (great, nifty): call a_function (bo, great, ri, nifty, ng) Mel. -- http://mail.python.org/mailman/listinfo/python-list
How to pass a global variable to a module?
Dear Python users, I just start to use python and love this language. I met this problem when I try to save my functions in a separate file. The question is how I can pass a global variable to a function which is saved in another file. If I save the function I defined in the same file with the main program, there is no problem after I declare the global variable. But problem comes out when I save all the function is a separate file. Help is very much appreciated! Thanks! Jinbo -- http://mail.python.org/mailman/listinfo/python-list
Re: How to pass a global variable to a module?
Hi, Am Tue, 29 Sep 2009 09:40:29 -0700 (PDT) schrieb Mars creature jin...@gmail.com: I just start to use python and love this language. I met this problem when I try to save my functions in a separate file. The question is how I can pass a global variable to a function which is saved in another file. If I save the function I defined in the same file with the main program, there is no problem after I declare the global variable. But problem comes out when I save all the function is a separate file. Help is very much appreciated! Thanks! Jinbo http://mail.python.org/pipermail/tutor/2002-November/018353.html -- Gregor http://gregor-horvath.com -- http://mail.python.org/mailman/listinfo/python-list
Re: How to pass a global variable to a module?
Mars creature wrote: Dear Python users, I just start to use python and love this language. I met this problem when I try to save my functions in a separate file. The question is how I can pass a global variable to a function which is saved in another file. If I save the function I defined in the same file with the main program, there is no problem after I declare the global variable. But problem comes out when I save all the function is a separate file. Help is very much appreciated! Thanks! Jinbo Do not use global variable, that's evil ! in file1.py: myVar = 'foo' in file2.py: import file1 print file1.myVar 'foo' file1.myVar = 'bar' print file1.myVar 'bar' Keep your variables ordered on their shelf. JM -- http://mail.python.org/mailman/listinfo/python-list
Re: How to pass a global variable to a module?
On Tue, 29 Sep 2009 09:40:29 -0700, Mars creature jin...@gmail.com wrote: Dear Python users, I just start to use python and love this language. I met this problem when I try to save my functions in a separate file. The question is how I can pass a global variable to a function which is saved in another file. If I save the function I defined in the same file with the main program, there is no problem after I declare the global variable. But problem comes out when I save all the function is a separate file. Help is very much appreciated! Thanks! Jinbo In Python, as in many other languages, I'd advise that you think about whether your variable needs to be global, or whether you could (or should) simply pass the variable to the function as a parameter. HTH, Rami -- Rami Chowdhury Never attribute to malice that which can be attributed to stupidity -- Hanlon's Razor 408-597-7068 (US) / 07875-841-046 (UK) / 0189-245544 (BD) -- http://mail.python.org/mailman/listinfo/python-list
Re: How to pass a global variable to a module?
On Sep 29, 12:49 pm, Rami Chowdhury rami.chowdh...@gmail.com wrote: On Tue, 29 Sep 2009 09:40:29 -0700, Mars creature jin...@gmail.com wrote: Dear Python users, I just start to use python and love this language. I met this problem when I try to save my functions in a separate file. The question is how I can pass a global variable to a function which is saved in another file. If I save the function I defined in the same file with the main program, there is no problem after I declare the global variable. But problem comes out when I save all the function is a separate file. Help is very much appreciated! Thanks! Jinbo In Python, as in many other languages, I'd advise that you think about whether your variable needs to be global, or whether you could (or should) simply pass the variable to the function as a parameter. HTH, Rami -- Rami Chowdhury Never attribute to malice that which can be attributed to stupidity -- Hanlon's Razor 408-597-7068 (US) / 07875-841-046 (UK) / 0189-245544 (BD) Thank you guys for the prompt and helpful response. From the link Gregor posted, it seems no way to share variable between modules. I can understand the point that global variables tends to mess up programs. Assume that I have 10 parameters need to pass to the function. If these parameters are fixed, I can use another module to store these 10 parameters, and import to the module, as suggested by jean-michel. But what if these 10 parameters will be changed in the main program? Passing the variable to the function as a parameter suggested by Rami will certainly do, but I am wondering weather there are other ways. What you'd like to code it? Thank you very much! Jinbo -- http://mail.python.org/mailman/listinfo/python-list
Re: How to pass a global variable to a module?
Mars creature wrote: On Sep 29, 12:49 pm, Rami Chowdhury rami.chowdh...@gmail.com wrote: On Tue, 29 Sep 2009 09:40:29 -0700, Mars creature jin...@gmail.com wrote: Dear Python users, I just start to use python and love this language. I met this problem when I try to save my functions in a separate file. The question is how I can pass a global variable to a function which is saved in another file. If I save the function I defined in the same file with the main program, there is no problem after I declare the global variable. But problem comes out when I save all the function is a separate file. Help is very much appreciated! Thanks! Jinbo In Python, as in many other languages, I'd advise that you think about whether your variable needs to be global, or whether you could (or should) simply pass the variable to the function as a parameter. HTH, Rami -- Rami Chowdhury Never attribute to malice that which can be attributed to stupidity -- Hanlon's Razor 408-597-7068 (US) / 07875-841-046 (UK) / 0189-245544 (BD) Thank you guys for the prompt and helpful response. From the link Gregor posted, it seems no way to share variable between modules. I can understand the point that global variables tends to mess up programs. Assume that I have 10 parameters need to pass to the function. If these parameters are fixed, I can use another module to store these 10 parameters, and import to the module, as suggested by jean-michel. But what if these 10 parameters will be changed in the main program? Passing the variable to the function as a parameter suggested by Rami will certainly do, but I am wondering weather there are other ways. What you'd like to code it? If there are a lot of them then an alternative is to pass them in some sort of contains, such as a dict or an object: class Params(object): pass params = Params() params.x = 'foo' params.x 'foo' -- http://mail.python.org/mailman/listinfo/python-list
Re: How to pass a global variable to a module?
Mars creature wrote: I just start to use python and love this language. I met this problem when I try to save my functions in a separate file. The question is how I can pass a global variable to a function which is saved in another file. This question is somewhat mis-phrased. In Python, one uses names -- local, nonlocal, global, and dotted -- as well as other expressions, to pass objects to functions as arguments that get bound to the parameter names of the function. Objects are neither local or global; they just are. Thinking this way will help your use of Python. If I save the function I defined in the same file with the main program, there is no problem after I declare the global variable. But problem comes out when I save all the function is a separate file. Help is very much appreciated! Thanks! Specific answers require specific examples and either a clear description of actual versus expected behavior or a complete copy of an error traceback. Good luck. tjr -- http://mail.python.org/mailman/listinfo/python-list
Re: How to pass a global variable to a module?
Mars creature wrote: snip I can understand the point that global variables tends to mess up programs. Assume that I have 10 parameters need to pass to the function. If these parameters are fixed, I can use another module to store these 10 parameters, and import to the module, as suggested by jean-michel. But what if these 10 parameters will be changed in the main program? Passing the variable to the function as a parameter suggested by Rami will certainly do, but I am wondering weather there are other ways. What you'd like to code it? Thank you very much! Jinbo If we're just talking generalities, we can give you general advice. Avoid globals like the plague. Except for constants, each global should require a lot of justification to permit its use. There's no harm in passing 10 parameters to a function. And if some of them are related to each other, group them in a tuple, or an object. If two functions seem to have a need to share data without passing it back and forth, they probably belong in a class. Most of the justifiable globals are already there in the standard libraries, or at least a good analogy. For example, stdout is used by print, wherever it occurs. Likewise you may want a global logging object. These are things which act a lot like constants, even though they have internal state. DaveA -- http://mail.python.org/mailman/listinfo/python-list
Re: How to pass a global variable to a module?
Mars creature jin...@gmail.com wrote:
Assume that I have 10 parameters need to pass to the function. If
these parameters are fixed, I can use another module to store these 10
parameters, and import to the module, as suggested by jean-michel. But
what if these 10 parameters will be changed in the main program?
With Python, for the duration of program execution a module is
(generally) only ever imported by an import statement once. Any other
imports will instead look up the result of the first import, and will
refer to that module.
So you can use modules to stash variables for the life of the program:
a.py:
import globals
globals.a = 1
globals.b = 2
b.py:
import globals
globals.b = 77
c.py:
import globals
print globals.a, globals.b # will be '1, 77'
Passing the variable to the function as a parameter suggested by Rami
will certainly do, but I am wondering weather there are other ways.
What you'd like to code it?
While you can use globals to avoid having to pass functions around,
it's generally a sign of bad code. You're tightly binding the
behaviour of the function to the presence of the globals, which makes
the function a lot harder to re-use elsewhere.
Depending on the functions, I'd tend to use either a list or a dict:
def positional_args_func(a, b, c, d, e):
... pass
...
params = [1, 3, 5, 7, 9]
positional_args_func(*params) # the * unpacks the list
def keyword_args_func(a=None, b=None, c=None, d=None, e=None):
... pass
...
params = dict(a=1, b=3, c=5, d=7, e=9)
keyword_args_func(**params) # the ** unpacks the dict
If you're using Python 2.6/3.x, you might find namedtuple handy:
from collections import namedtuple
Parameters = namedtuple('Parameters', 'a b c d e')
params = Parameters(1, 3, 5, 7, 9)
params
Parameters(a=1, b=3, c=5, d=7, e=9)
params.a, params.e
(1, 9)
def singular_arg_func(params):
... # access through params.a, params.b etc
... pass
...
singular_arg_func(params)
Or course, any combination of these can be used in the same functions.
Hope this helps.
--
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