Matching Permutations of Two Lists In Python   

When you have a long list and want to create permutations that match the length of a shorter list, you're essentially creating partial permutations or k-permutations.

The Problem

Given:

• Long list: [A, B, C, D, E] (5 items)
• Short list: [X, Y] (2 items)

You want permutations of the long list with length 2.

Python Solutions

1: Using itertools.permutations()

from itertools import permutations

long_list = ['A', 'B', 'C', 'D', 'E']
short_list = ['X', 'Y']

result = list(permutations(long_list, len(short_list)))
print(result[:5])  # First 5 results

Output:
[('A', 'B'), ('A', 'C'), ('A', 'D'), ('A', 'E'), ('B', 'A')]

2: Manual approach with nested loops

long_list = ['red', 'blue', 'green', 'yellow']
short_list = ['item1', 'item2', 'item3']

result = []
for i in range(len(long_list)):
    for j in range(len(long_list)):
        for k in range(len(long_list)):
            if i != j != k != i:  # Ensure no duplicates
                result.append((long_list[i], long_list[j], long_list[k]))
                if len(result) >= 10:  # Limit for demo
                    break
        if len(result) >= 10:
            break
    if len(result) >= 10:
        break

print(result)

[('red', 'blue', 'green'), ('red', 'blue', 'yellow'), ('red', 'green', 'blue'), ('red', 'green', 'yellow'), ('red', 'yellow', 'blue'), ('red', 'yellow', 'green'), ('blue', 'red', 'green'), ('blue', 'red', 'yellow'), ('blue', 'green', 'red'), ('blue', 'green', 'yellow')]

Real-World Examples

1: Team Selection

from itertools import permutations

players = ['Alice', 'Bob', 'Charlie', 'Diana', 'Eve']
positions = ['Captain', 'Vice-Captain']  # 2 positions to fill

team_combinations = list(permutations(players, len(positions)))
print(f"Possible leadership teams: {len(team_combinations)}")

Output is 20 combinations (5×4):

[('Alice', 'Bob'),
 ('Alice', 'Charlie'),
 ('Alice', 'Diana'),
 ('Alice', 'Eve'),
 ('Bob', 'Alice'),
 ('Bob', 'Charlie'),

2: Color Combinations

colors = ['red', 'blue', 'green', 'yellow', 'purple']
design_slots = ['primary', 'secondary', 'accent']  # 3 slots

color_schemes = list(permutations(colors, len(design_slots)))
print(f"Total color schemes: {len(color_schemes)}")

Output: 60 combinations (5×4×3)

[('red', 'blue', 'green'),
 ('red', 'blue', 'yellow'),
 ('red', 'blue', 'purple'),
 ('red', 'green', 'blue'),
 ('red', 'green', 'yellow'),
 ('red', 'green', 'purple'),
 ('red', 'yellow', 'blue'),

Key Points

• Formula: For n items choosing k positions = n!/(n-k)!
• Order matters: (A,B) ≠ (B,A)
• No repetition: Each item used only once per permutation
• Memory warning: Large lists create many combinations quickly

Quick Reference

# Get k-length permutations from n-length list
from itertools import permutations
result = list(permutations(long_list, len(short_list)))

This approach works for any scenario where you need ordered selections from a larger set matching a target length.