Function Call Variables Same as In Function

Question

I am somewhat new to Python--beginner moving to intermediate--and would like to know how more experienced Python coders name their call and function variables.

Specifically, I like to name the call variables the same as the called function's 'receive' variables. Ditto the return variables.

Works fine, but are there problems I could run into, outside of changing a variable to global in the future?

An example call: v_Array = f_InitSpecified2DArray(v_Width,v_Length) The example called or 'receiving' function: def f_InitSpecified2DArray(v_Width, v_Length): And I do the same in the return as well: return v_Array

def f_InitSpecified2DArray(v_Width, v_Length):
    v_Array = [v_Width, v_Length]
    return v_Array

v_Array = f_InitSpecified2DArray(v_Width,v_Length)

The question is: Shall I expect any conflict resulting from reuse of name v_Array inside the function return and later in the calling code, where it goes assigned into variable with the same name v_Array?

Thanks.

Answer 1

No, this will not cause you difficulties, and doesn't cause confusion - for you, your readers, or the Python interpreter. Certainly it's less confusing than making up a new name just to differ from the parameter name, which is unnecessary. In fact, you'll often encounter the same name being used for both a named parameter and its argument, as in

runner = DocTestRunner(verbose=verbose, optionflags=optionflags)

which comes from doctest.py in the standard library (for Python 3.3).

It's instructive to search the standard library for this pattern, <name>=<same_name> (abuse of notation which I'll rectify in a moment), as its occurrences are examples of just what you're asking about. On OS X and Linux, the following command will show all lines in the standard library (plus site-packages) with occurrences of the pattern:

grep -Er --include=*.py '(\b[[:alnum:]]+\b)=\1\b' /path/to/pythonlib

On a Mac, for example, /path/to/pythonlib for Python 3.3 is usually /Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3.

This command shows how many lines feature the construct, many of which have multiple occurrences:

grep -Er --include=*.py '(\b[[:alnum:]]+\b)=\1\b' /path/to/pythonlib | wc -l

I get a count of 1129, which includes a few dozen in my site-packages subdirectory. In other words, it's quite common.

Answer 2

Read PEP 008 titled "Style Guide for Python Code"

You seem to search for something more precise and systematic, this I appreciate, but you will safe a lot of effort and confusion to yourself and others dealing with your code, if you try to folow the PEP 008.

As usual, you will not find it followed everywhere, but that is life.

To your question about function names and variables - PEP 008 recommends using lowercase names with words separated by underscore.

local variable names are irrelevant, it really does not matter what variable name you use for return.

And do not plan moving variables into global scope too early, you shall in fact working in the other direction.