How to Generate All 3‑Item Combinations in Python Using itertools and List Comprehensions

1. Introduction

A fan asked for a Python solution to a basic permutation‑combination problem. The task is to compute the number of ways to choose 3 items from a list of 10, which mathematically equals C(10,3)=120.

2. Implementation

Method 1: Using itertools.combinations

from itertools import combinations
word = ['鲁班七号','鲁班','鲁班大师','甄姬','安琪拉','王昭君','韩信','孙悟空','程咬金','猪八戒']
res = [i for i in combinations(word, 3)]
print(res)
print(len(res))

The output shows 120 combinations, matching the manual calculation.

Method 2: Custom index‑based approach (illustrated in the image below)

This method also yields 120 combinations but requires pre‑computing the order of elements.

Method 3: List comprehension with slicing

word = ['鲁班七号','鲁班','鲁班大师','甄姬','安琪拉','王昭君','韩信','孙悟空','程咬金','猪八戒']
res = [[i, j, k] for i in word[:] for j in word[word.index(i)+1:] for k in word[word.index(j)+1:]]
print(res)
print(len(res))

The result image confirms 120 combinations.

Method 4: Explicit three‑level loop

res = []
for i in word[:]:
    for j in word[word.index(i)+1:]:
        for k in word[word.index(j)+1:]:
            res.append([i, j, k])
print(res)

The corresponding output again shows 120 combinations.

3. Conclusion

All three implementations correctly generate the 120 three‑item combinations, matching the manual calculation. For larger data sets, the itertools.combinations approach is recommended because it is concise and efficient.