Python：沒有。字符串中的每個字符的出現次數的

Question

可能重複：
how to get the number of occurrences of each character using python

什麼是獲得一個字符串的每個字符的數量和存儲它的最佳方式（我使用一本字典 - 這種選擇會有很大的不同嗎？）？我想到了幾個方法：

1.

for character in string: 
    if character in characterCountsDict: 
     characterCountsDict[character] += 1 
    else: 
     characterCountsDict[character] = 1 

2.

character = 0 
while character < 127: 
    characterCountsDict[str(unichr(character))] = string.count(str(unichr(character)) 
    character += 1 

我認爲第二種方法比較好... 但要麼是他們的好？ 有沒有更好的方法來做到這一點？

Answer 1

如果你有興趣的最有效的方式，它似乎是這樣的：

from collections import defaultdict 

def count_chars(s): 
    res = defaultdict(int) 
    for char in s: 
     res[char] += 1 
    return res 

時序：

from collections import Counter, defaultdict 

def test_counter(s): 
    return Counter(s) 

def test_get(s): 
    res = {} 
    for char in s: 
     res[char] = res.get(char, 0) + 1 
    return res 

def test_in(s): 
    res = {} 
    for char in s: 
     if char in res: 
      res[char] += 1 
     else: 
      res[char] = 1 
    return res 

def test_defaultdict(s): 
    res = defaultdict(int) 
    for char in s: 
     res[char] += 1 
    return res 


s = open('/usr/share/dict/words').read() 
#eof 

import timeit 

test = lambda f: timeit.timeit(f + '(s)', setup, number=10) 
setup = open(__file__).read().split("#eof")[0] 
results = ['%.4f %s' % (test(f), f) for f in dir() if f.startswith('test_')] 
print '\n'.join(sorted(results)) 

結果：

0.8053 test_defaultdict 
1.3628 test_in 
1.6773 test_get 
2.3877 test_counter 

Answer 2

>>> from collections import Counter 
>>> Counter("asdasdff") 
Counter({'a': 2, 's': 2, 'd': 2, 'f': 2}) 

注意，您可以使用Counter的物體，像字典。