如何在Python中获取字符串的所有字母排列及其大小写？

Question

如何在Python中获取一个字符串的所有可能的字母大小写组合？

举个例子：

输入：'ab' 输出：'aB', 'Ba', 'BA', 'Ab', 'AB', 'bA'

输入：'dan' 输出：'aND', 'ANd', 'Dna', 'naD', 'DaN', 'aDn', 'Adn', 'dnA', 'NdA', 'anD', 'DnA', 'NAD', 'nAD', 'Dan', 'NDA', 'nAd', 'AdN', 'DAn', 'AnD', 'And', 'DNA', 'daN', 'adN', 'nDa', 'dAN', 'dNa', 'aDN', 'ADN', 'dNA', 'Nda', 'AND', 'DNa', 'NaD', 'Nad', 'aNd', 'nDA', 'dAn', 'NAd', 'ndA', 'NDa', 'ADn', 'DAN'

Answer 1

把 itertools.permutations 和 itertools.product 结合起来：

from itertools import permutations, product

def perm_with_case(word):
    cased = product(*zip(word.lower(), word.upper()))
    next(cased) # throw away the all-lowercase result
    return (''.join(p) for w in cased for p in permutations(w))

得到的结果是

>>> list(perm_with_case("ab"))
['aB', 'Ba', 'Ab', 'bA', 'AB', 'BA']
>>> list(perm_with_case("dan"))
['daN', 'dNa', 'adN', 'aNd', 'Nda', 'Nad', 'dAn', 'dnA', 'Adn', 'And', 'ndA', 'nAd', 'dAN', 'dNA', 'AdN', 'ANd', 'NdA', 'NAd', 'Dan', 'Dna', 'aDn', 'anD', 'nDa', 'naD', 'DaN', 'DNa', 'aDN', 'aND', 'NDa', 'NaD', 'DAn', 'DnA', 'ADn', 'AnD', 'nDA', 'nAD', 'DAN', 'DNA', 'ADN', 'AND', 'NDA', 'NAD']

这个结果看起来符合我们想要的输出，虽然我承认我不太明白为什么要把全小写的值去掉。

Answer 2

你可以使用itertools.product这个函数来实现。想了解更多，可以去看看这个链接：https://docs.python.org/2/library/itertools.html

这里有个例子：

def combos(s):
    combolist = []
    for i in range(len(s)):
        combolist.append([])
    for i in range(len(s)):
        combolist[i].append(s[i].lower())
        combolist[i].append(s[i].upper())
    return list(itertools.product(*combolist))

输出结果是：

combos('ab')
>>> [('a', 'b'), ('a', 'B'), ('A', 'b'), ('A', 'B')]
combos('dan')
>>> [('d', 'a', 'n'), ('d', 'a', 'N'), ('d', 'A', 'n'), ('d', 'A', 'N'), ('D', 'a', 'n'), ('D', 'a', 'N'), ('D', 'A', 'n'), ('D', 'A', 'N')]

从这里开始，你可以很容易地进行格式化。

Answer 3

这可以通过使用itertools来实现。

from itertools import permutations
def perm(word):
    perms = [''.join(p) for p in permutations(word)]
    print(perms)
    return perms

def capPer(arrPerm):
    result=[]
    for val in arrPerm:
        wordList=list(val)

        for i,letter in enumerate(wordList):
            wordList[i]=letter.upper()
            result.extend(perm(''.join(wordList)))
    return set(result)

def combi(wrd):
    print(capPer(perm(wrd)))


combi('ab')
combi('dan')

**output:**
set(['aB', 'Ba', 'BA', 'Ab', 'AB', 'bA'])
set(['aND', 'ANd', 'Dna', 'naD', 'DaN', 'aDn', 'Adn', 'dnA', 'NdA', 'anD', 'DnA', 'NAD', 'nAD', 'Dan', 'NDA', 'nAd', 'AdN', 'DAn', 'AnD', 'And', 'DNA', 'daN', 'adN', 'nDa', 'dAN', 'dNa', 'aDN', 'ADN', 'dNA', 'Nda', 'AND', 'DNa', 'NaD', 'Nad', 'aNd', 'nDA', 'dAn', 'NAd', 'ndA', 'NDa', 'ADn', 'DAN'])