Python Growth notes

Regular expressions

1. Select a match: Pipe symbol (|), which means " choose one from multiple modes ". Example:at|home à at,home

2. dot matches any character except line break

3. boundary match:\b matches the boundary of a word;\b matches in the middle of a word, which is not the word boundary.

4. Character set: matches any character that is contained in the square brackets. applies only to single-character cases . Example:[ab] àa,b

5. An asterisk (*) matches 0 or more occurrences of its left side

A plus (+) match occurs one or more times

Question Mark (?) Match 0 or one occurrence

6. Character Set special character:\d to match any decimal number

                              \w The character set

that represents all letters

\s represents a space character

Note: The uppercase representation of special characters does not match, example:\d represents any non-decimal digits

!--[if!supportlists]-->7. parentheses specify grouping and matching subgroups, for example: (\w+)-(\d+)

!--[if!supportlists]-->8. match objects: group () and groups ().

!--[if!supportlists]-->9.group (): either return the entire match, or return a specific subgroup as required; groups () returns only one tuple that contains a unique or all child group.

!--[if!supportlists]-->10. !--[Endif]-->match () and search () Difference: match () starts from the beginning of the string, search () will not only search the starting part, but strictly search the string from left to right.

!--[if!supportlists]-->11. !--[Endif]-->findall () The full non-repetition of a regular expression pattern in the query string, the returned is a list .

!--[if!supportlists]-->12. The!--[Endif]-->finditer () is with findall ( similar but more memory-saving entities. Difference: .

!--[if!supportlists]-->13. The!--[Endif]--> search and replace: Sub () and subn ()

　　is some form of substitution for all the parts of a string that match a regular expression. Difference:subn () also returns a total number that represents the substitution.

Function

!--[if!supportlists]-->1.*args

!--[if!supportlists]-->2.**kwargs dict form

3. Parameters:

Normal parameters: Pass the arguments to the formal parameter in strict order

Default parameter: Must be placed at the end of the parameter list

Specify parameter: assigns a parameter to the specified formal parameter

Dynamic Parameters:* Default incoming parameters, all placed in tuples

                ** default incoming parameters, all placed in the dictionary

Universal parameters: *args, * * Kwargs

!--[if!supportlists]-->4.python .

5. variables:

Global variables, all scopes are readable.

To re-assign a global variable, you need global, such as:Global name

Special, the list, dictionary, can be modified, but not re-assigned value.

Global variables are uniformly capitalized.

6. a shorthand for the if else for ternary operations (Trinocular operations)

Example: Name = ' Alex ' if  1==1  Else ' SB '

　　

Python Growth notes