python: how to change the value of function's input parameter?

Question

I tried to modify the value of a string inside a function, like below:

>>> def appendFlag(target, value):
...     target += value
...     target += " "
...
>>> appendFlag
<function appendFlag at 0x102933398>
>>> appendFlag(m,"ok")
>>> m
''

Well, seems the "target" is only changed within the function, but how to make the new value viable outside the function? Thanks.

Answer 1

This is handled in python by returning.

def appendFlag(target, value):
   target += value
   target += " "
   return target

you can use it like this:

m = appendFlag(m,"ok")

you can even return several variables like this:

def f(a,b):
   a += 1
   b += 1
   return a,b

and use it like this:

a,b = f(4,5)

Answer 2

You need to use an object that can be modified

>>> m = []
>>> def appendFlag(target, value):
...     target.append(value)
...     target.append(" ")
...
>>> appendFlag(m, "ok")
>>> m
['ok', ' ']