python 可以任意生成我想要的字典例如4位数字或者2位英文的所有组合不重复

生成4位数字的所有组合，不重复：

digits = '0123456789'
combinations = {}
for i in digits:
    for j in digits:
        for k in digits:
            for l in digits:
                combination = i + j + k + l
                if combination not in combinations:
                    combinations[combination] = True
print(combinations.keys())

生成2位英文的所有组合，不重复：

import string

letters = string.ascii_lowercase
combinations = {}
for i in letters:
    for j in letters:
        combination = i + j
        if combination not in combinations:
            combinations[combination] = True
print(combinations.keys())
``