[Python Basics] str string, pythonstr string

[Python Basics] str string, pythonstr string

The str string is an unchangeable object.

1. Create a string

S1 = str () # create an empty string s2 = str ("hello") # create a string "hello"

 

2. Common functions and operations for processing strings (1). Functions

Len ()	Returns the number of characters in a string.
Max ()	Returns the largest character in a string.
Min ()	Returns the smallest character in a string.

>>>s = "Welcome">>>len(s)7>>>max(s)'o'>>>min(s)'W'

 

The full text of string s is common and will not be described below

(2) The range of the subscript operator [] s [index] index is [0, len (s)-1]. Note: python allows negative numbers to be the most subscript.

>>>print(s[6], s[4])e o>>>print(s[-1], s[-3])e o

 

(3 ). the Truncation operator [start: end] [start: end] intercepts and returns a string whose subscript starts from start to end-1 in string s. If start> end, an empty string is returned.

>>> S [] 'elc' >>> s [1:-1] # You can also use the negative 'elcom' >>> s [3: -8] # truncate and return an empty string''

 

(4). Join operator + and copy operator * +: connect two strings. -: Copy strings.

>>> S1 = "hello" >>> s2 = "world" >>> s1 + ''+ s2 'Hello world' >>> 3 * s1 # and s1 * 3 same as 'hellohellohellohel'

 

(5). Determine whether a string is in another string (in and not in). For example, s is the string "Welcome"

>>> 'Come in s # if it is true, tureTrue is returned >>> 'cat' in s # If it is false, falseFalse is returned >>> 'cat' not in sTrue

 

(6). Comparison string (= ,! =,>, <, >=, <=) Python compares characters in strings. Start from the first character. If the first character is the same, the second character is compared, and so on. If the expression is True, True is returned; otherwise, False is returned.

>>> S1 = 'integer' >>> s2 = 'int' >>> s1 = s2False >>> the ARCII code value of s1 <s2 # 'E' is greater than 0, therefore, falseFalse >>> s1 >=s2true is returned.

 

(7). substring generation string (with for loop) yi generation string s:

>>> for ch in s:    print(ch)    Welcome>>> 

3. Other strings (1). Test strings

Isalnum (): bool	Returns true if the string is a letter or number and has at least one character.
Isalpha (): bool	Returns true if the string is a letter and has at least one character.
Isdigit (): bool	Returns true if the string contains only numeric characters.
Isdentifier (): bool	Returns true if the string is a python identifier.
Islower (): bool	Returns true if all characters in the string are lowercase and contain at least one character.
Isupper (): bool	Returns true if all characters in the string are uppercase and contain at least one character.
Isspace (): bool	Returns true if all characters in the string are spaces and contain at least one character.

(2). SEARCH strings

Startswitch (s1: str): bool	Returns true if the substring is s1.
Endswitch (s1: str): bool	Returns true if the string ends with a substring of s1.
Find (s1): int	Returns the lowest subscript of s1 in the string.-1 is returned if no subscript exists.
Rfind (s1): int	Returns the highest subscript of s1 in the string.-1 is returned if no subscript exists.
Count (sub string): int	Returns the number of times that the substring appears in the string.

(3). Convert the string

Capitalize (): str	Returns the copied string with the first character in uppercase.
Lower (): str	Returns the copied string and converts all the letters to lowercase letters.
Upper (): str	Returns the copied string and converts all letters to uppercase letters.
Title (): str	Returns the copied string and capital the first letter of each word.
Swapcase (): str	Returns the copied string, converts uppercase letters to lowercase letters, and converts lowercase letters to uppercase letters.
Replace (old, new): str	Returns the new string, and replaces all old strings with new.

(4). Delete spaces in the string

Lstrip (): str	Returns the substring that removes the front-end blank string.
Rstrip (): str	Returns the substring that removes the backend blank string.
Strip (): str	Returns the substring that removes the empty strings at both ends.

(5). format the string

Center (width): str	Returns a string copy centered on a given width field.
Ljust (width): str	Returns the left-aligned string text in the given width field.
Must ust (width): str	Returns the right-aligned string text in the given width field.
Format (items): str