Python Lambda Problems
Question: What's going on here? I'm trying to create a list of functions:

    
    
    def f(a,b):
        return a*b
    
    funcs = []
    
    for i in range(0,10):
        funcs.append(lambda x:f(i,x))
    

This isn't doing what I expect. I would expect the list to act like this:

    
    
    funcs[3](3) = 9
    funcs[0](5) = 0
    

But all the functions in the list seem to be identical, and be setting the
fixed value to be 9:

    
    
    funcs[3](3) = 27
    funcs[3](1) = 9
    
    funcs[2](6) = 54
    

Any ideas?


Answer: lambdas in python are closures.... the arguments you give it aren't going to
be evaluated until the lambda is evaluated. At that time, i=9 regardless,
because your iteration is finished.

The behavior you're looking for can be achieved with functools.partial

    
    
    import functools
    
    def f(a,b):
        return a*b
    
    funcs = []
    
    for i in range(0,10):
        funcs.append(functools.partial(f,i))
    

