python正则表达式

1.简单python匹配和正则寻找配对

# 导入模块
import re

# 简单python 匹配
## match  string
pattern1 = "cat"
pattern2 = "bird"
string = "dog runs to cat"

print(pattern1 in string) #True
print(pattern2 in string) #False

# 用正则寻找配对
pattern1 = "cat"
pattern2 = "bird"
string = "dog runs to cat"
print(re.search(pattern1, string))
print(re.search(pattern2, string))

2.匹配多种可能

# 匹配多种可能使用[]
#multiple patterns ("ran" or "run")
ptn = r"r[au]n" # 考虑两种情况在一起
print(re.search(ptn, "dog runs to cat"))

3.匹配更多可能

# 导入模块
import re

print(re.search(r"r[A-Z]n", "dog runs to cat"))
print(re.search(r"r[a-z]n", "dog runs to cat"))
print(re.search(r"r[0-9]n", "dog r2ns to cat"))
print(re.search(r"r[0-9a-z]n", "dog runs to cat"))

4. 数字

# 导入模块
import re

# \d:decimal digit
print(re.search(r"r\dn", "run r4n"))
# \D:any non-decimal digit
print(re.search(r"r\Dn", "run r4n"))

5. 空白符

# 导入模块
import re

# \s: any white space [\t\n\r\f\v]
print(re.search(r"r\sn", "r\nn r4n"))
# \S: opposite to \s, any non-white space
print(re.search(r"r\Sn", "r\nn r4n"))

6. 所有字母数字和"_"

# 导入模块
import re

# \w: [a-zA-Z0-9_]
print(re.search(r"r\wn", "r\nn r4n"))
# \W: opposite to \w
print(re.search(r"r\Wn","r\nn r4n"))

7. 空白格

8. 特殊字符

9. 句首句尾

10. 是否

11. 多行匹配

将每一行看作单独一行

12. 0或多次

13. 1或多次

14. 出现多次次数

15. group组

16. 寻找所有匹配

17. 替换

18. 分裂

19. compile