x=5
def printx()
print x
x=10
running this gives unboundlocal error
but when my function is just print x i get no error..
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Related: http://stackoverflow.com/questions/1188944/reason-for-unintuitive-unboundlocalerror-behaviour – Sven Marnach Feb 04 '11 at 18:41
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1Duplicate of http://stackoverflow.com/questions/1281184/why-cant-i-set-a-global-variable-in-python – Sven Marnach Feb 04 '11 at 18:45
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@Benjamin: That is true but the missing `:` is not the reason for the error. – user225312 Feb 04 '11 at 18:46
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possible duplicate of [Global variables in Python](http://stackoverflow.com/questions/423379/global-variables-in-python) – Matti Virkkunen Feb 04 '11 at 18:47
1 Answers
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Simply assigning a value to x in the function is making it a local variable, therefore shadowing the global x = 5 specified on the previous line. And on the line you're trying to print x, the local version of x hasn't been initialized yet. It is curious how doing something on a later line is influencing lines that come before it, but that's just how it works.
You don't need any special declaration to read a global variable, therefore it works without the assignment inside the function. However, if you'd rather assign 10 to the global x instead of making a new, local x, you'll have to specify global x inside the function.
Matti Virkkunen
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