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Name: [002] Ian Ozsvald
Member: 128 months
Authored: 181 videos
Description: I am the co-founder of ShowMeDo (see, author of `The Screencasting Handbook <>`_ and the founder of the professional screencast production company `ProCasts <>`_: .. image:: ...

Variable Scope [ID:923] (5/6)

in series: Python Beginners - Functions

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The scope for variables is important - variables can only be 'seen' in their correct scope. New programmers might find this a bit confusing, these examples should make the basic scope rules of Python clear.

We use three examples to show how scope works, how masking works (which you want to avoid) and how globals can be used to change the scope rules. I also explain why global should be avoided.

Link: global

# Variable Scope using Python 2.5
# 2008/10/22

def scope1():
    "Scope example using local scope."
    print "in scope1"
    a = 1
    print a
    print "finished scope1"
#print a # will cause error

#b = 2
#def scope2_masking_existing_variable():
#    "Scope example with masking."
#    print "in scope2"
#    b = 3 # this b masks the external b, can't be seen outside
#    # NOTE this is a possible cause of error in your program
#    # design, you might do this thinking that the change to
#    # b is reflected once the function finishes - it won't be!
#    print b
#    print "finished scope2"
#print b    
#print b # has the value 2

#c = 2
#def scope3_using_global():
#    "Scope example using global to access external variable."
#    #global c
#    #
#    # NOTE globals make it harder to figure out where
#    # your variables were declared
#    # This can make debugging harder therefore not recommended
#    print "in scope3"    
#    print c # error as c is not in the local scope (yet)
#    c = 4 
#    print c # c is 4
#    print "finished scope2"
#print c
#print c # has the value 4

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Excellent video on globals/scope since I am coming from C language

Good info and demo for a beginner like myself.

Hi Gasto. The video runs for 10:19 on my machine with a cleaned cache, that's the correct length.

Can you clear your cache and try again please?



The video keeps finishing before its true end.

The ShowMeDo Robot says - this video is now published, thanks for adding to ShowMeDo.

Your video has been edited. This is an automatic post by ShowMeDo.

Showmedo is a peer-produced video-tutorials and screencasts site for free and open-source software (FOSS)- with the exception of some club videos, the large majority are free to watch and download.

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Educating the Open-source Community With Showmedo

Although as important as the software it supports, education and documentation are relatively neglected in the Open-source world. Coders love to code, and explaining how best to use or improve the software tends to be deferred or even sidelined.

At Showmedo we believe the community can play a vital role here and also say thanks for the tools and software that make our lives easier. If you have a piece of software you love or a programming langugage you are enthusiastic about, why not make a screencast showing others how to use it? All the stuff you wish you'd been told, the tips, tricks, insights that would have saved you time and frustration.

Screencasting is easier than you think, and we're happy to help you. You can emailus for advice or just use some of the how-to screencasts on the site. This screencasting learning-pathis a good place to start.

Kudos and Thanks for Ian

3 Minute Oveview (What Does Python Look Like?)

simple and informative. you draw me in
70 months ago


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