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This article mainly shows you the "Python regular expression knowledge points", the content is easy to understand, clear, hope to help you solve your doubts, the following let Xiaobian lead you to study and learn "Python regular expression knowledge points what are there" this article.

1. The special character "\ d" is very commonly used, which means numbers. The code demonstrates as shown in the following figure.

Where "+" means continuous, and here it means continuous numbers. But the output only has the character "4", due to greedy mode, which was also mentioned in the previous article.

2. If you want to match "2004", you need to add a special character "?", as shown in the following figure.

This is a non-greedy mode, the matching takes place from the back to the back, and matches consecutive numbers, so the output is "2004".

3. Another common use is to use curly braces to specify the length of matching digits, as shown in the following figure, specifying that the matching number length is 4, that is, consecutive 4 digits.

Today, the editor will take you to review these 10 articles about the special characters of regular expressions, but will not expand them in detail.

1. "^" means to be limited to start with a certain character. For specific usage, please refer to this article: Python regular expression beginners (1).

2. "*" means to limit the occurrence of the preceding character any number of times, which includes 0 times, that is, the number of times is greater than or equal to 0. Specific usage can refer to this article: Python regular expression first acquaintance (1).

3. It means any character, and it has a very wide range, including all the characters. Specific usage can refer to this article: Python regular expression first acquaintance (1).

4. "$" means to limit the end to a certain character. For specific usage, please refer to this article: the first knowledge of Python regular expressions (2).

5. "?" It means non-greedy mode. For specific usage, please refer to this article: the first knowledge of Python regular expressions (2).

6. "+" means to limit the occurrence of the preceding character any number of times, which does not include 0 times, at least once, that is, the number of times is greater than or equal to 1. Specific usage can refer to this article: Python regular expression first acquaintance (3).

7. The three expressions of "{2}", "{2,}" and "{2pm 5}" limit the number of occurrences of the preceding character. "{2}" represents that the preceding character appears twice; "{2,}" represents that the preceding character appears more than twice; "{2jin5}" represents that the preceding character appears between two and five times. Specific usage can refer to this article: Python regular expression first acquaintance (4).

8. "|" means that the values on both sides of the vertical bar only need to match one of them to meet the requirements, which is equivalent to the "OR" in the logical operation relationship. For specific usage, please refer to this article: Python regular expression beginnings (5).

9. There are three expressions: "[]", "[A-Za-z0-9]" and "[^]". "[]" indicates any character that appears in parentheses; "[A-Za-z0-9]" indicates the range of values; "[^]" means right or wrong. Specific usage can refer to this article: Python regular expression first acquaintance (6).

10. "\ s" means to represent spaces, and "\ S" means to represent non-spaces. For specific usage, please refer to this article: Python regular expression beginnings (7).

11. "\ w" means 26 uppercase and lowercase letters, 10 numbers from 0 to 9, and an underscore, that is, what the expression [A-Za-z0-9] represents; "\ W" means the opposite of "\ w" and represents all characters except what the expression [A-Za-z0-9] represents. For specific usage, please refer to this article: the first knowledge of Python regular expressions (8).

12. The interval "[\ u4E00 -\ u9FA5]" means Chinese characters. Specific usage can refer to this article: Python regular expression first acquaintance (9).

13. "()" is used to extract substrings and is mentioned in every article on regular expressions.

14. "\ d" means to represent a numeric type. For specific usage, please refer to this article.

These are all the contents of the article "what are the knowledge points of Python regular expressions?" Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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