6.2.7 Example: Word Counts

• Script that builds a dictionary to count the number of occurrences of each word in a tokenized string.
• Python automatically concatenates strings separated by whitespace in parentheses.

# fig06_02.py
"""Tokenizing a string and counting unique words."""

text = ('this is sample text with several words '
        'this is more sample text with some different words')

word_counts = {}

# count occurrences of each unique word
for word in text.split():
    if word in word_counts: 
        word_counts[word] += 1  # update existing key-value pair
    else:
        word_counts[word] = 1  # insert new key-value pair

print(f'{"WORD":<12}COUNT')

for word, count in sorted(word_counts.items()):
    print(f'{word:<12}{count}')

print('\nNumber of unique words:', len(word_counts))

run fig06_02.py

WORD        COUNT
different   1
is          2
more        1
sample      2
several     1
some        1
text        2
this        2
with        2
words       2

Number of unique words: 10

Python Standard Library Module collections

• The Python Standard Library already contains the counting functionality shown above.
• A Counter is a customized dictionary that receives an iterable and summarizes its elements.

from collections import Counter

text = ('this is sample text with several words '
        'this is more sample text with some different words')

counter = Counter(text.split())

for word, count in sorted(counter.items()):
    print(f'{word:<12}{count}')
    

different   1
is          2
more        1
sample      2
several     1
some        1
text        2
this        2
with        2
words       2

print('Number of unique keys:', len(counter.keys()))

Number of unique keys: 10

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