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#1
February 22nd, 2004, 05:40 AM
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Making closures in loop ?
Hi there,
I want to create a list of functions with something like: closures = [lambda x: i*x for i in range(10)] so that closures[0] = 0*x closures[1] = 1*x closures[2] = 2*x ... closures[9] = 9*x For some reason, all elements seem to bind the last value of i, that is closures[j] = 9*x for all j, not only 9. Any ideas of why does this happen, and how should I make it work as intended ? George
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#2
February 22nd, 2004, 05:47 AM
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#3
February 22nd, 2004, 06:10 AM
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You can get it to work the way you want by passing in i as a default parameter, i.e.:
Code:
>>> closures = [lambda x, i=i: i*x for i in range(10)] >>> closures[1](2) 2 >>> closures[4](2) 8 This was the standard way to simulate closures in Python prior to 2.1, when it did not have the new scoping rules. Dave - The Developers' Coach
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#4
February 22nd, 2004, 11:28 AM
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I was sure there was a way around it; thanks a lot Dave !
George
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