[portland] Alternatives to Globals for passing information between methods.

[Andrew Lorente]

Hi Viraj,

I think your idea #2--putting these methods on an object and making num1/2
be attributes of it--is the way to go. However, #3 is probably easier than
you'd guess. Python lets you return a tuple and then break up the returned
tuple in the calling code. This makes it really easy to define functions
that return multiple values, without having to write up a big ol' data
structure to hold those values:

>>> def foo():
...     return (1, 'a')
...
>>> (val1, val2) = foo()
>>> val1
1
>>> val2
'a'

Here's that notion applied to the relevant bits of your code:

def captureInput():
    # Capture Input - Get the 2 numbers to be checked for connectivity.
    # Remember to do a file based parsing logic for the same.
*    # (the `global` declaration has been removed)*
    Num1 = int(raw_input('First Number: ').rstrip('\n'))
    Num2 = int(raw_input('Second Number: ').rstrip('\n'))
    print "Checking (", num1, ",", num2, ")"
*    return (Num1, Num2)
*
def main():
    userResponseFlag = 1
    while userResponseFlag:
        userResponse = raw_input('Do you want to check connectivity between
2 given numbers - answer(y/n) only: ')
        if userResponse == 'y':
*             (Num1, Num2) = captureInput()*
            doConnectivityCheck(Num1, Num2)
            storeInput(Num1, Num2)
        elif userResponse == 'n':
            userResponseFlag = 0
        else:
            print "Your input does not confirm to the y/n rule, fix that
and retry"
            continue


However, I think making Num1 and 2 instance attributes will prove to be
more convenient.

Hope this helps!

Andrew

On Sat, Jul 28, 2012 at 11:28 PM, Viraj Sharma <virajbsharma at gmail.com>wrote:

> All,
>    I was recently introduced to programming, so this is really a beginner's
> query. Let me know if this is not the right mailing list for that. I will
> switch it accordingly. Anyway to my query:
>
> I have heard that the "Globals are bad for programming" -  (
> http://c2.com/cgi/wiki?GlobalVariablesAreBad). Keeping that in mind, I
> need
> to change my solution from below to something more elegant.
>
> Can someone let me know the best solution for sharing the values of Num1
> and Num2 in the example given below. From my perspective 3 options came
> into my mind when I coded this
>
> #1. Was to use Globals (Num1 and Num2) to pass variable values between the
> various methods.
>
> #2. Was to create an object and have Num1 and Num2 defined as class member
> variables. In that case, the value of these variables could be used across
> multiple methods defined on that class.
>
> #3. Was to use an array/list type data structure, store the Num1 and Num2
> values in it and then return that structure everytime I want to expose the
> value of Num1 and Num2 between various method calls.
>
> It is possible that there maybe more elegant solutions. But I quite frankly
> do not know how to decide. Therefore requesting help ...
>
>
> ===================================================
> #!/usr/bin/env python
>
> __author__ = 'vsharma'
>
> Num1 = 0
> Num2 = 0
>
> def captureInput():
>     # Capture Input - Get the 2 numbers to be checked for connectivity.
>     # Remember to do a file based parsing logic for the same.
>     global Num1, Num2
>     Num1 = int(raw_input('First Number: ').rstrip('\n'))
>     Num2 = int(raw_input('Second Number: ').rstrip('\n'))
>     print "Checking (", num1, ",", num2, ")"
>
> def doConnectivityCheck(Num1, Num2):
>     # I have removed the actual code for simplicity
>     print "The following 2 numbers are connected (", Num1, ",", Num2, ")"
>
>     return
>
> def storeInput(Num1, Num2):
>     # I have removed the actual code for simplicity
>     print "The following 2 numbers have been stored (", Num1, ",", Num2,
> ")"
>     return
>
> def main():
>     userResponseFlag = 1
>     while userResponseFlag:
>         userResponse = raw_input('Do you want to check connectivity between
> 2 given numbers - answer(y/n) only: ')
>         if userResponse == 'y':
>             captureInput()
>             doConnectivityCheck(Num1, Num2)
>             storeInput(Num1, Num2)
>         elif userResponse == 'n':
>             userResponseFlag = 0
>         else:
>             print "Your input does not confirm to the y/n rule, fix that
> and retry"
>             continue
>
> main()
> ===================================================
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