Python's Enumerate Function

Python's enumerate function is an awesome tool that allows us to create a counter alongside values we're iterating over: as part of a loop, for example.

enumerate takes an iterable type as its first positional argument, such as a list, a string, or a set, and returns an enumerate object containing a number of tuples: one for each item in the iterable. Each tuple contains an integer counter, and a value from the iterable.

enumerate also takes an optional additional parameter called start, which can be provided as either a keyword or positional argument. If no start value is provided, enumerate begins counting from zero, making it a perfect tool for tracking the index of each item.

The most common place to find enumerate being used is within something like a for loop, with the tuples inside the enumerate object destructured into two separate loop variables.

friends = ["Rolf", "John", "Anna"]

for counter, friend in enumerate(friends, start=1):
	print(counter, friend)

# 1 Rolf
# 2 John
# 3 Anna

The use of enumerate is not limited to just for loops, however; we can also make use of enumerate as part of a list comprehension, for example, or even passed in as an argument to dict.

friends = ["Rolf", "John", "Anna"]
friends_dict = dict(enumerate(friends))  # {0: 'Rolf', 1: 'John', 2: 'Anna'}

Wrapping up

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