Source: Python Morsels

Description

Given an iterable and an item, strip any leading elements of the iterable that are equivalent to that item. Return remaining data as an iterator.

The item may be a function, in which case strip leading elements of the iterable that cause the function to return true when passed as an argument.

Notes

Use itertools/dropwhile.

My solution

Here, a factory function provides the appropriate evaluation. Use callable() to detect a function passed as an argument.

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def test_item(iter, item):
    if callable(item):
        def test(first):
            return item(iter[first])
    else:
        def test(first):
            return item == iter[first]
    return test


def lstrip(iter, item):
    iter = list(iter)
    iterlen = len(iter)
    if not iterlen:
        return []

    test = test_item(iter, item)
    first = 0
    try:
        while test(first) and first < iterlen:
            first += 1
    except IndexError:
        pass

    return (item for item in iter[first:])

Provided solution

Much more compact and elegant.

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from itertools import dropwhile

def lstrip(iterable, strip_value):
    if callable(strip_value):
        predicate = strip_value
    else:
        def predicate(value):
            return value == strip_value
    return dropwhile(predicate, iterable)