'while' in list comprehension?

[Skip Montanaro]

    >> foo = [ i for i in bar while len(i)>0 ]

    Emile> How is this different from:

    Emile>      foo = [ i for i in bar if len(i) ]

The first is like:

    _ = []
    for i in bar:
        if not (len(i) > 0):
           break
        _.append(i)
    return _

The second is like:

    _ = []
    for i in bar:
        if len(i) > 0:
            _.append(i)
    return _

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