Type Check Problem

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February 5th, 2013, 12:24 AM

CastorTroy

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Join Date: Feb 2013

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Type Check Problem

Quick question...

I want to add up elements in a list...pretty simple. But when some of those elements are nested lists, I want to add those up also. And then add the sum of the nested lists to the sum of the original list.

For example:

Code:

nested_list = [3, 43, 1, [11, 15, 3, 23, 2], [6, 4, 1, 88], [12, 53, 96]]

total = 0
for nested in nested_list:
    if nested == type(list):
        x = sum(nlist)
        total += x
        print(total)
    else:
        total += nested
        print(total)

When the code hits the first nested list I get the "unsupported operand type" error.
Why is it skipping over the if and going to the else?
Any help is much appreciated. Thanks

February 5th, 2013, 01:47 AM

SuperOscar

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Quote:

Originally Posted by CastorTroy

Code:

    if nested == type(list):

When the code hits the first nested list I get the "unsupported operand type" error.

A slight mistake. You meant:

Code:

    if type(nested) == type(list):

Actually, though, the recommended way is:

Code:

    if isinstance(nested, list):

In any case, your solution works only on two levels (there is no true recursion), but I guess that’s no problem?

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February 5th, 2013, 10:27 AM

b49P23TIvg

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Someone recently mentioned lisp, thus

Code:

def car(L):
    return L[0]

def cdr(L):
    return L[1:]

def flatten(L):
    '''
        >>> flatten([3,4,[43,34,[23,2423]]])
        [3, 4, 43, 34, 23, 2423]
        >>> flatten(3)
        [3]
        >>> flatten([])
        []
    '''
    if isinstance(L,str):
        return [L]
    if hasattr(L,'__len__'):
        if 0 == len(L):
            return []
        return flatten(car(L)) + flatten(cdr(L))
    return [L]

print(sum(flatten([3, 43, 1, [11, 15, 3, 23, 2], [6, 4, 1, 88], [12, 53, 96]])))

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