Python從門到精通(一):基礎-05-RE正規表達式

一、查找模式

import re

pattern = 'this'
text = 'Does this text match the pattern?'

match = re.search(pattern, text)

s = match.start()
e = match.end()

print('Found "{}"\nin "{}"\nfrom {} to {} ("{}")'.format(
    match.re.pattern, match.string, s, e, text[s:e]))
    
Found "this"
in "Does this text match the pattern?"
from 5 to 9 ("this")      

二、編譯模式

import re

# Precompile the patterns
regexes = [
    re.compile(p)
    for p in ['this', 'that']
]
text = 'Does this text match the pattern?'

print('Text: {!r}\n'.format(text))

for regex in regexes:
    print('Seeking "{}" ->'.format(regex.pattern), end=' ')#end是個格式化輸出，預設是換行，這處不換行 

    if regex.search(text):
        print('match!')
    else:
        print('no match')
# Text: 'Does this text match the pattern?'
# 
# Seeking "this" -> match!
# Seeking "that" -> no match      

三、簡單示例

3.1、修改字元串

import re

bold = re.compile(r'\*{2}(.*?)\*{2}')
text = 'Make this **bold**.  This **too**.'
print('Text:', text)
print('Bold:', bold.sub(r'<b>\1</b>', text))
# Bold: Make this <b>bold</b>.  This <b>too</b>.      

3.2、拆分字元串

import re

text = '''Paragraph one
on two lines.

Paragraph two.


Paragraph three.'''

for num, para in enumerate(re.findall(r'(.+?)\n{2,}',
                                      text,
                                      flags=re.DOTALL)
                           ):
    print(num, repr(para))
    print()
    # 0 'Paragraph one\non two lines.'
    #
    # 1 'Paragraph two.'