Most Common Word

Write a function that finds the most frequently occurring word in a string.

most_common_word(text)

Words are separated by single spaces. If there's a tie, return whichever of the tied words appears first in text. Use collections.Counter.

Examples

most_common_word("the cat sat on the mat the cat ran")  // → "the"   (appears 3 times)
most_common_word("a a b b b c")                           // → "b"     (appears 3 times)
most_common_word("x y z")                                 // → "x"     (all tied, x is first)

Walkthrough

Thinking it through

from collections import Counter


def most_common_word(text):
    counts = Counter(text.split())
    return counts.most_common(1)[0][0]

text.split() breaks the string into a list of words. Counter(...) takes that list and builds a count of how many times each word appears — this is the exact "counting dict" pattern you might build by hand with a regular dict, done for you in one call.

counts.most_common(1) returns a list containing the single most frequent entry, as a (word, count) tuple — for "the cat sat on the mat the cat ran", that's [("the", 3)]. Indexing [0] gets that one tuple, and [0] again gets the word out of the tuple (index 0 of ("the", 3) is "the"; index 1 would be the count 3).

Why ties resolve the way they do

When multiple words are tied for the most common, most_common() breaks the tie by insertion order — the word that was counted first (i.e., appeared first in the original text) comes first in the result. That's why "x y z" (all appearing once, all tied) returns "x": it's simply the first one Counter encountered while scanning the text.

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