使用字典计算字符串中的第一个字母 - Python

Question

我一直在 Python 进行字典练习，我对语言和编程本身还很陌生。我一直在尝试获取一个字符串或字符串列表，让我的代码比较字符串的第一个字母，并根据有多少字符串以字母表中的某个字母开头来制作字典。这是我目前所拥有的：

  d = {}
text=["time","after","time"]
# count occurances of character
for w in text:

    d[w] = text.count(w)
# print the result
for k in sorted(d):
    print (k + ': ' + str(d[k]))

我的目标是获得以下结果：

count_starts(["time","after","time"]) -->{'t':  2,  'a':    1}

但是，我得到的更像是以下内容：

count_starts(["time","after","time"]) --> {time:2, after:1}

利用我所拥有的，我已经能够计算整个唯一字符串出现的次数，而不仅仅是计算字符串中的第一个字母。

我还尝试了以下方法：

d = {}
text=["time","after","time"]
# count occurances of character
for w in text:
    for l in w[:1]:
        d[l] = text.count(l)
# print the result
for k in sorted(d):
    print (k + ': ' + str(d[k]))

但是在打印输出中给我的是：

{"a":0,"t":0}

我正在使用 Python Visualizer 进行测试。

Answer 1

计算文本中每一项首字母出现的次数：

from collections import Counter

text = ["time", "after", "time"]

>>> Counter(t[0] for t in text)
Counter({'a': 1, 't': 2})

或者只是获取字典 key/value 对：

>>> dict(Counter(t[0] for t in text))
{'a': 1, 't': 2}

Answer 2

d = {}

text = ['time', 'after', 'time']

for w in text:
    if w:                         # If we have the empty string. w[0] Does not Exist (DNE)
        if w[0] in d:             # Check to see if we have first character in dictionary.
            d[w[0]] = d[w[0]] + 1 # Use the first character as key to dictionary.
        else:                     # If character has not been found start counting.
            d[w[0]] = 1           # Use the first character as key to dictionary.

使用 Python 的 IDLE 我得到：

>>> d = {}
>>> text = ['time', 'after', 'time']
>>> for w in text:
    if w:
        if w[0] in d:
            d[w[0]] = d[w[0]] + 1
        else:
            d[w[0]] = 1

>>> print d
{'a': 1, 't': 2}
>>>

使用字典计算字符串中的第一个字母 - Python

Using Dictionaries to Count First Letter in a String - Python

python

string

dictionary

letter