python - How to take the first N items from a generator or list?

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Answer 1

Slicing a list

top5 = array[:5]

• To slice a list, there's a simple syntax: array[start:stop:step]
• You can omit any parameter. These are all valid: array[start:], array[:stop], array[::step]

Slicing a generator

import itertools
top5 = itertools.islice(my_list, 5) # grab the first five elements

• You can't slice a generator directly in Python. itertools.islice() will wrap an object in a new slicing generator using the syntax itertools.islice(generator, start, stop, step)

• Remember, slicing a generator will exhaust it partially. If you want to keep the entire generator intact, perhaps turn it into a tuple or list first, like: result = tuple(generator)