(Python) Should I use parameters or make it global?

Question

I have many functions that all share the same parameter. They will be inputting and outputting this parameter many times.

For example:

a = foo
a = fun(a)
a = bar(a)

def fun(a):
     ...
     return a

def bar(a):
     ...
     return a

What is more pro-grammatically correct, passing parameters through a function, or having it be globally accessible for all the functions to work with?

a = foo
fun()
bar()

def fun():
    global a
    ...

def bar():
    global a
    ...

Using arguments makes it MUCH easier to reuse the code. If the functions are all related and work on similar data, you could also consider making a class to bundle everything together. This is also highly resuable. — kindall, Aug 24 '17 at 19:30
You better pass an object and manipulate the fields in that case. — Willem Van Onsem, Aug 24 '17 at 19:31
I strongly discourage the use of globals. They are seldom used in practice. — Alexander, Aug 24 '17 at 19:35
Whenever you find yourself thinking "should I use a global?", default to "no". — user2357112, Aug 24 '17 at 19:35

score 6 · Answer 1 · answered Aug 24 '17 at 19:36

The more localised your variables, the better.

This is virtually an axiom for any programming language.

structs in C (and equivalents in other languages such as FORTRAN) grew up from this realisation, and object orientated programming followed shortly after.

score 5 · Accepted Answer · answered Aug 24 '17 at 19:34

5

For re-usability of method, passing parameter is better way.

answered Aug 24 '17 at 19:34

Dharmesh Fumakiya

2,276
2
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Is there a point where it is unreasonable to pass many parameters? – tisaconundrum Aug 24 '17 at 19:35
3

@tisaconundrum you can always wrap your data in a container or object, and pass that, instead of multiple arguments... – juanpa.arrivillaga Aug 24 '17 at 19:42

bouletta · Answer 3 · 2017-08-24T19:56:16.340

2

I agree with the other answers but just for the sake of completion, as others have pointed out a class sounds like a good idea here. Consider the following.

class myClass(object):
    def __init__(self, foo):
        self.a = foo

    def fun(self):
        # do stuff to self.a

    def bar(self):
        # do something else to self.a 

c = myClass(foo)
c.fun()
c.bar()

edited Aug 24 '17 at 19:56

answered Aug 24 '17 at 19:47

bouletta

525
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(Python) Should I use parameters or make it global?

3 Answers3

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