python - 如何计算代码中关键字的出现次数，但忽略注释/文档字符串中的关键字？

Question

我对 Python 还很陌生。我想在下面的代码中找到 Python 关键字 ['def','in', 'if'...] 的出现次数。但是，需要忽略代码中任何字符串常量中找到的关键字。 如何计算关键字出现次数而不计算字符串中的关键字？

def grade(result):
    '''
    if if (<--- example to test if the word "if" will be ignored in the counts)
    :param result: none
    :return:none
    '''

    if result >= 80:
        grade = "HD"
    elif 70 <= result:
        grade = "DI"
    elif 60 <= result:
        grade = "CR"
    elif 50 <= result:
        grade = "PA"
    else:
    #else (ignore this word)
        grade = "NN"
    return grade

result = float(raw_input("Enter a final result: "))

while result < 0 or result > 100:
    print "Invalid result. Result must be between 0 and 100."
    result = float(raw_input("Re-enter final result: "))

print "The corresponding grade is", grade(result)

Answer 1

使用tokenize、keyword和collections模块。

tokenize.generate_tokens(readline)

The generate_tokens() generator requires one argument, readline, which must be a callable object which provides the same interface as the readline() method of built-in file objects (see section File Objects). Each call to the function should return one line of input as a string. Alternately, readline may be a callable object that signals completion by raising StopIteration.

The generator produces 5-tuples with these members: the token type; the token string; a 2-tuple (srow, scol) of ints specifying the row and column where the token begins in the source; a 2-tuple (erow, ecol) of ints specifying the row and column where the token ends in the source; and the line on which the token was found. The line passed (the last tuple item) is the logical line; continuation lines are included.

New in version 2.2.

import tokenize
with open('source.py') as f:
    print list(tokenize.generate_tokens(f.readline))

部分输出:

[(1, 'def', (1, 0), (1, 3), 'def grade(result):\n'),
 (1, 'grade', (1, 4), (1, 9), 'def grade(result):\n'),
 (51, '(', (1, 9), (1, 10), 'def grade(result):\n'),
 (1, 'result', (1, 10), (1, 16), 'def grade(result):\n'),
 (51, ')', (1, 16), (1, 17), 'def grade(result):\n'),
 (51, ':', (1, 17), (1, 18), 'def grade(result):\n'),
 (4, '\n', (1, 18), (1, 19), 'def grade(result):\n'),
 (5, '    ', (2, 0), (2, 4), "    '''\n"),
 (3,
  '\'\'\'\n    if if (<--- example to test if the word "if" will be ignored in the counts)\n    :param result: none\n    :return:none\n    \'\'\'',
  (2, 4),
  (6, 7),
  '    \'\'\'\n    if if (<--- example to test if the word "if" will be ignored in the counts)\n    :param result: none\n    :return:none\n    \'\'\'\n'),
 (4, '\n', (6, 7), (6, 8), "    '''\n"),
 (54, '\n', (7, 0), (7, 1), '\n'),
 (1, 'if', (8, 4), (8, 6), '    if result >= 80:\n'),

您可以从keyword模块检索关键字列表:

import keyword
print keyword.kwlist
print keyword.iskeyword('def')

与集合的集成解决方案。计数器:

import tokenize
import keyword
import collections 
with open('source.py') as f:
    # tokens is lazy generator
    tokens = (token for _, token, _, _, _ in tokenize.generate_tokens(f.readline))
    c = collections.Counter(token for token in tokens if keyword.iskeyword(token))

print c  # Counter({'elif': 3, 'print': 2, 'return': 1, 'else': 1, 'while': 1, 'or': 1, 'def': 1, 'if': 1})