5 Best Ways to Find Common Words Among Tuple Strings in Python

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πŸ’‘ Problem Formulation: In Python, you may encounter a problem where you need to find common words among a collection of strings stored within a tuple. Imagine a tuple containing descriptions or phrases where we want to extract the intersection of words across these elements. For example, given a tuple ('apple mango banana', 'banana orange apple', 'berry banana apple'), the desired output are the words that are common to all strings, such as ['apple', 'banana'].

Method 1: Using Sets and Set Intersection

This method involves converting each string in the tuple to a set of words and then performing set intersection to find the common words among them. Sets in Python are collections that automatically remove duplicate entries and provide efficient operations for set comparisons like intersection, difference, and union.

Here’s an example:

tuples = ('apple mango banana', 'banana orange apple', 'berry banana apple')
common = set(tuples[0].split())
for s in tuples[1:]:
    common &= set(s.split())

print(sorted(common))

Output:

['apple', 'banana']

This code snippet first splits the first tuple string into words and converts it into a set. Then, it iterates over the rest of the tuple elements, continually updating the set with the intersection of the current set and the next set of words. The result is a set of words that are common to all tuple strings.

Method 2: Using functools.reduce with Set Intersection

This involves using Python’s functools.reduce() function to apply the set intersection operation across all strings in the tuple. The reduce() function is meant for performing a computation on a list by applying a reducing function to each item cumulatively.

Here’s an example:

from functools import reduce

tuples = ('apple mango banana', 'banana orange apple', 'berry banana apple')
common = reduce(lambda acc, s: acc & set(s.split()), tuples, set(tuples[0].split()))

print(sorted(common))

Output:

['apple', 'banana']

The reduce function takes a lambda that performs the intersection, a tuple to be reduced, and the initial value of the accumulator, which is the set of words from the first string in the tuple. This function reduces the tuple to a single set containing common words.

Method 3: Using List Comprehension and Set Intersection

This method utilizes the list comprehension feature in Python to create sets of words from each string in the tuple and then calculate the intersection of all generated sets.

Here’s an example:

tuples = ('apple mango banana', 'banana orange apple', 'berry banana apple')
sets = [set(s.split()) for s in tuples]
common = set.intersection(*sets)

print(sorted(common))

Output:

['apple', 'banana']

We begin by breaking down the tuple into a list of sets. We then use the set.intersection() method with argument unpacking to find the common elements. This line of code succinctly captures the words common among the tuple strings.

Method 4: Using Counter from collections module

Counting occurrences of each word across strings with Collections.Counter() and selecting only those with occurrences equal to the number of strings in the tuple can give us the common words.

Here’s an example:

from collections import Counter

tuples = ('apple mango banana', 'banana orange apple', 'berry banana apple')
word_count = Counter(word for s in tuples for word in s.split())
common = [word for word, count in word_count.items() if count == len(tuples)]

print(common)

Output:

['apple', 'banana']

The Counter object word_count holds the frequency of each word across all strings. The list comprehension then filters out the words that appear as many times as there are strings in the tuple. Consequently, the resulting list contains only the common words.

Bonus One-Liner Method 5: Using Generator Expression and Set Intersection

A concise one-line alternative is possible by using a generator expression within the set.intersection() method.

Here’s an example:

tuples = ('apple mango banana', 'banana orange apple', 'berry banana apple')
common = set.intersection(*(set(s.split()) for s in tuples))

print(sorted(common))

Output:

['apple', 'banana']

This one-liner combines the ideas of set intersection and generator expressions. It performs the intersection on the fly, avoiding the need for an additional line of code to create the sets.

Summary/Discussion

  • Method 1: Using Sets and Set Intersection. Strengths: Simple and uses native Python operations. Weaknesses: Not the most compact syntax.
  • Method 2: Using functools.reduce with Set Intersection. Strengths: Efficient one-liner fold operation. Weaknesses: Can be less readable for those unfamiliar with reduce().
  • Method 3: Using List Comprehension and Set Intersection. Strengths: Very readable and Pythonic. Weaknesses: Requires intermediate list of sets.
  • Method 4: Using Counter from collections module. Strengths: Offers more information (word count) which can be useful in other contexts. Weaknesses: Overhead of creating a Counter object and less direct for finding just the common words.
  • Method 5: Using Generator Expression and Set Intersection. Strengths: Extremely concise. Weaknesses: Less explicit, which might affect readability for some users.