Shulou(Shulou.com)06/03 Report--

This article focuses on "how to use regular expressions in python". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor learn "how to use regular expressions in python".

I. Preface

When we do interface automation, when dealing with the relevant data that the interface depends on, we usually use regular expressions to extract the relevant data.

Regular expressions are used in python, which can be implemented using the official library re.

Second, the use of re module

To use regular expressions in python, you need to use the re module to operate. Here we introduce several methods commonly used in the re module.

01 re.match function

Parameter description: receive two parameters

The first ① is the matching rule.

The second ② is the matching target string

Re.match attempts to match a pattern from the beginning of the string.

If the match is successful, a matching object (which contains our matching information) is returned.

Match () returns null if the starting position match is not successful.

Case study:

02 re.search method

Parameter description: receive two parameters

The first ① is the matching rule.

The second ② is the matching target string

Re.search scans the entire string and returns the first successful match.

Case study:

The difference between re.match and re.search:

① re.match matches from the beginning of the string. If the beginning of the string does not conform to the regular expression, the match fails and the function returns empty.

② and re.search match the entire string and return it until a successful match is found. If no successful match is found in the whole string, empty is returned.

03 findall method

Parameter description: receive two parameters

The first ① is the matching rule.

The second ② is the matching target string

Finds all the substrings matched by the regular expression in the string and returns a list, or an empty list if no matches are found.

Case study:

Note: match and search match one result, and findall matches all the results that conform to the rules.

04 sub method

To replace some characters in a string, you can use regular expressions to match the selected substring.

Parameters:

Pattern: matching rules

Repl: new content to be replaced after matching

String: a string that needs to be replaced by rules

Count: the number of replacements. Parameters may not be passed, and all those that conform to the rules can be replaced by default.

Case study:

05 greed mode explains

Greedy mode: the default quantifier in Python is greedy, always trying to match as many characters as possible

The following are examples:

There is a string s, we need to match more than 3 numbers in the string, there are 8 numbers in the string, greedy pattern will match as many characters as possible, more than 3, 8 is also more than 3, so the matching result here is 8 numbers.

Non-greedy mode: always try to match as few characters as possible. Add? after "*", "?", "+", "{mforce n}", {m,} to turn off greedy mode.

After turning off greed mode, get as little as possible.

As follows, only the first three values are obtained (at least 3 in the case of rules, non-greedy is to match the first three arrays that conform to the rules)

About the re module, more usage, this article does not do too much introduction, everyone to study, thank you!

The basic matching of regular expressions is attached for your reference.

Third, regular expression grammar

01 represents a single character

Single character: represents a single character, such as\ d for matching numbers and\ D for matching non-digits.

The specific rules are as follows:

02 indicates quantity

If you want to match a character multiple times, you can add a quantity after the character to represent it.

The specific rules are as follows:

03 represents the boundary

Used to indicate the boundaries of a string or word, such as the beginning of a string, the beginning of a word, etc.

04 matching grouping

Group the matching content.

At this point, I believe you have a deeper understanding of "how to use regular expressions in python". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.