7.18 Regular Expressions Summary

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Python Regular Expressions

 

Regular expressions are a special character sequence, it can help you to easily check whether a string matches a pattern.

 

re.match function

re.match attempts string from the starting position to match a pattern matching the start position if not successful, match () returns none.

 

grammar:

 

re.match(pattern, string, flags=0)

 

pattern ---> matching regular expression

string ---> string to match

flags ---> flags to control the regular expression matching mode

 

 

 

re.search method

re.search scan the entire string and returns the first successful match.

 

 

grammar:

 re.match(pattern,string, flags=0)

 

pattern ---> matching regular expression

string ---> string to match

flags ---> flags to control the regular expression matching mode

 

Search and replace

 

re.sub(pattern,rep1,string,count=0,flags=0)

 

parameter:

• pattern: in a regular pattern string.
• repl: replace the string, it may be a function.
• string: find the original string to be replaced.
• count: Maximum number of replacements of the pattern matching, default 0 means to replace all occurrences.

 

 

re.compile function

function is used to compile a regular expression compiler generates a regular expression (the Pattern) object for match () and search () function uses these two.

 

re.compile(pattern[,flags])

 

parameter:

• pattern: a string of regular expression

• the flags: optional, represent the matching pattern, such as ignoring the case, multi-line mode, for the specific parameters:

  1. re.I  ignore case
  2. re.L  represent special characters \ w, \ W, \ b , \ B, \ s, \ S depends on the current environment
  3. re.M  multiline mode
  4. re.S  that is  . and include any character, including newline ( not included newline)
  5. re.U  represent special characters \ w, \ W, \ b , \ B, \ d, \ D, \ s, \ S depends on the Unicode character properties database
  6. re.X  To increase readability, ignoring whitespace and  comments back #

 

 

findall

Find expression in the string being matched by all the sub-strings , and returns a list , if no match is found, it returns an empty list.

Note:  match and search is a match findall match all.

 

 

findall(string[, pos[, endpos]])

 

 

pattern = Re . the compile ( R & lt ' \ D + ' ) # find a number

result1 = pattern.findall('runoob 123 google 456')

result2 = pattern.findall('run88oob123google456', 0, 10)

print(result1)

print(result2)

Output:

['123', '456'] ['88', '12']

 

 

re.finditer

And findall Similarly, the string is found in the positive expression matched all substrings, and returns them as an iterator.

 

 

re.finditer(pattern, string, flags=0)

Import reality it = reality . Cleave ( R " \ d + " , " 12a32bc43jf3 " )

for match in it:

　　 print (match.group() )

Output:

12 
32 
43 3

.	Matches any single character except "\ n" is. To match include '\ n', including any character, like the use of '[. \ N]' mode.
\d	Matches a digit character. Equivalent to [0-9].
\D	Matching a non-numeric characters. It is equivalent to [^ 0-9].
\s	Matches any whitespace characters, including spaces, tabs, page breaks, and so on. Is equivalent to [\ f \ n \ r \ t \ v].
\S	匹配任何非空白字符。等价于 [^ \f\n\r\t\v]。
\w	匹配包括下划线的任何单词字符。等价于'[A-Za-z0-9_]'。
\W	匹配任何非单词字符。等价于 '[^A-Za-z0-9_]'。

[Pp]ython	匹配 "Python" 或 "python"
rub[ye]	匹配 "ruby" 或 "rube"
[aeiou]	匹配中括号内的任意一个字母
[0-9]	匹配任何数字。类似于 [0123456789]
[a-z]	匹配任何小写字母
[A-Z]	匹配任何大写字母
[a-zA-Z0-9]	匹配任何字母及数字
[^aeiou]	除了aeiou字母以外的所有字符
[^0-9]	匹配除了数字外的字符