Count occurrences of an element in a list in Python

To count one item, use the list's count() method. To count every item, use Counter from the collections module.

The program

from collections import Counter

votes = ["red", "blue", "red", "green", "blue", "red"]

print("Votes for red:", votes.count("red"))

counts = Counter(votes)
print(counts)
print("Winner:", counts.most_common(1))
print("Votes for purple:", counts["purple"])

Votes for red: 3
Counter({'red': 3, 'blue': 2, 'green': 1})
Winner: [('red', 3)]
Votes for purple: 0

How it works

• votes.count("red") looks through the whole list and counts the items equal to "red".
• Counter(votes) goes through the list once and builds a dictionary from each item to its count. If you call count() once for every different item, the list is read again each time. Counter reads it once.
• most_common(1) gives a list with the one most common item and its count, as a tuple.
• A Counter gives 0 for an item it has not seen. A normal dictionary would raise a KeyError.

Another way: a dictionary by hand

This is what Counter does for you:

votes = ["red", "blue", "red", "green", "blue", "red"]

counts = {}
for vote in votes:
    counts[vote] = counts.get(vote, 0) + 1

print(counts)

{'red': 3, 'blue': 2, 'green': 1}

counts.get(vote, 0) gives the current count, or 0 the first time a colour is seen.

Related programs: Frequency table from a list.