Question

脚本：

import re

matches = ['hello', 'hey', 'hi', 'hiya']

def check_match(string):
    for item in matches:
        if re.search(item, string):
            print 'Match found: ' + string
        else:
            print 'Match not found: ' + string

check_match('hey')
check_match('hello there')
check_match('this should not match')
check_match('oh, hiya')

输出：

Match not found: hey
Match found: hey
Match not found: hey
Match not found: hey
Match found: hello there
Match not found: hello there
Match not found: hello there
Match not found: hello there
Match not found: this should not match
Match not found: this should not match
Match found: this should not match
Match not found: this should not match
Match not found: oh, hiya
Match not found: oh, hiya
Match found: oh, hiya
Match found: oh, hiya

我不明白有各种各样的事情，对于初学者来说，每个字符串在这个输出中被搜索四次，一些返回两个作为找到的匹配，有三个。我不确定我的代码中有什么问题会导致这种情况发生，但是有人可以尝试看看有什么问题吗？

预期的输出是：

Match found: hey
Match found: hello there
Match not found: this should not match
Match found: oh, hiya

Answer 1

它的行为不正确，这是你对re.search(...)的误解。

查看输出后的评论：

Match not found: hey                    # because 'hello' is not in 'hey'
Match found: hey                        # because 'hey' is in 'hey'
Match not found: hey                    # because 'hi' is not in 'hey'
Match not found: hey                    # because 'hiya' is not in 'hey'

Match found: hello there                # because 'hello' is in 'hello there'
Match not found: hello there            # because 'hey' is not in 'hello there'
Match not found: hello there            # because 'hi' is not in 'hello there'
Match not found: hello there            # because 'hiya' is not in 'hello there'

Match not found: this should not match  # because 'hello' is not in 'this should not match'
Match not found: this should not match  # because 'hey' is not in 'this should not match'
Match found: this should not match      # because 'hi' is in 'this should not match'
Match not found: this should not match  # because 'hiya' is not in 'this should not match'

Match not found: oh, hiya               # because 'hello' is not in 'oh, hiya'
Match not found: oh, hiya               # because 'hey' is not in 'oh, hiya'
Match found: oh, hiya                   # because 'hi' is in 'oh, hiya'
Match found: oh, hiya                   # because 'hiya' is in 'oh, hiya'

如果您不希望在输入hi的情况下匹配模式oh, hiya，则应该在模式周围包含字边界：

\bhi\b

这将使其仅匹配由其他字母hi包围的well hiya there 而非的出现次数与{{1}不匹配但是\bhi\b 会）。

Answer 2

试试这个 - 它更简洁，它会标记多个匹配：

import re

matches = ['hello', 'hey', 'hi', 'hiya']

def check_match(string):
    results = [item for item in matches if re.search(r'\b%s\b' % (item), string)]
    print 'Found %s' % (results) if len(results) > 0 else "No match found"

check_match('hey')
check_match('hello there')
check_match('this should not match')
check_match('oh, hiya')
check_match('xxxxx xxx')
check_match('hello and hey')

给出：

Found ['hey']
Found ['hello']
No match found
Found ['hiya']
No match found
Found ['hello', 'hey']

Answer 3

你得到4个搜索和4个输出，因为你循环遍历一个数组，搜索并输出数组中每个元素的东西......

Answer 4

for循环是针对每个'匹配'检查字符串，并打印出找到或未找到的每个匹配。你真正想要的是查看任何匹配是否匹配，然后打印出一个“找到”或“未找到”。我实际上并不知道python，因此语法可能会关闭。

for item in matches:
    if re.search(item, string):
    found = true
if found:
    print 'Match found: ' + string
else:
    print 'Match not found: ' + string

`

正则表达式出乎意料

4 个答案: