[Python][Regular Expressions][正規表示式] Python’s Regex Symbols

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[Regular Expressions][正規表示式] Python’s Regex Symbols

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# Sample Code1:

import re

phoneNumRegex1 = re.compile(r'\d{3}-\d{3}-\d{4}')

mo1 = phoneNumRegex1.search('My number is 415-555-4242.')

print('Phone number found: ' + mo1.group())

# Phone number found: 415-555-4242

1. Grouping with Parentheses:  ( )

2. Matching Multiple Groups with the Pipe:  |  亦即 or

3. Optional Matching with the Question Mark: (wo)? 亦即 Optional = Match zero or one

4. Matching Zero or More with the Star: (wo)* 亦即 Match zero or more

5. Matching One or More with the Plus: (wo)+ 亦即 Match one or more (at least one)

6. Matching Specific Repetitions with Braces: {3}

7. The findall() Method: 回傳 list

8. Making Your Own Character Classes: [aeiouAEIOU]

# Sample Code2:

import re

vowelRegex = re.compile(r'[aeiouAEIOU]')

mo2 = vowelRegex.findall('RoboCop eats baby food. BABY FOOD.')

print(type(mo2))

# <class 'list'>

print(mo2)

# ['o', 'o', 'o', 'e', 'a', 'a', 'o', 'o', 'A', 'O', 'O']

9. The Caret (^ 跳脫符號: begin with) and Dollar Sign ($: end with) Characters

10. The Wildcard Character: . (dot) = wildcard 亦即 Match any character except for a new line.

11. Matching Everything with Dot-Star (.*): 

  dot .  表示: any single character except the newline

  star * 表示: zero or more of the preceding character

# Sample Code3:

import re

nameRegex = re.compile(r'First Name: (.*) Last Name: (.*)')

mo3 = nameRegex.search('First Name: Al Last Name: Amzshar')

print(mo3.group(1))

# 'Al'

print(mo3.group(2))

# 'Amzshar'

12. Matching Newlines with the Dot Character: newlineRegex = re.compile('.*', re.DOTALL) 

The  ?  matches zero or one of the preceding group.

The  *  matches zero or more of the preceding group.

The  +  matches one or more of the preceding group.

The  {n}  matches exactly n of the preceding group.

The  {n,}  matches n or more of the preceding group.

The  {,m}  matches 0 to m of the preceding group.

The  {n,m}  matches at least n and at most m of the preceding group.

{n,m}?  or  *?  or  +?  performs a non-greedy (also called lazy) match of the preceding group.

^spam  means the string must begin with spam.

spam$  means the string must end with spam.

The  .  (dot) = wildcard matches any character, except newline characters.

\d ,  \w , and  \s  match a digit, word, or space character, respectively.

\D ,  \W , and  \S  match anything except a digit, word, or space character, respectively.

[abc]  matches any character between the brackets (such as a, b, or c).

[^abc]  matches any character that isn’t between the brackets.

(1) Basic Syntax

(2) Regex Character Classes

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