help on understanding this output - Printable Version +- Python Forum (https://python-forum.io) +-- Forum: Python Coding (https://python-forum.io/forum-7.html) +--- Forum: General Coding Help (https://python-forum.io/forum-8.html) +--- Thread: help on understanding this output (/thread-2347.html) |
help on understanding this output - landlord1984 - Mar-08-2017 >>> flist = [] >>> for i in range(3): ... flist.append(lambda: i) ... >>> [f() for f in flist] # what will this print out?Why is the above output [2,2,2]? Thanks, L RE: help on understanding this output - zivoni - Mar-08-2017 Python uses "late binding" here. Lambda is defined with variable i, but actual value of i is looked up when that lambda is called. After for loop i is 2, so all lambdas return 2. Common trick to avoid this is to use such variable as another parameter: lambda x, i=i : x + i # <- this binds i to actual value of iIn your case lambda i=i : i would work as "expected".
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