python sequence basic operations

1. The following built-in function can be used for sequences (tables, fixed value tables, strings): s is a sequence
len(s) Returns: The number of elements contained in the sequence
min(s ) Returns: The smallest element in the sequence
max(s) Returns: The largest element in the sequence
all(s) Returns: True, if all elements are True
any(s) Returns: True, if any element is If True

2. The following method mainly functions as a query without changing the sequence itself, and can be used for tables and fixed value tables:
sum(s) Returns: the sum of all elements in the sequence

# x is the element value, i is Subscript (the position of the element in the sequence)
s.count(x) Returns: the number of times x appears in s
s.index(x) Returns: the subscript of the first occurrence of x in s

3. Since the elements of the fixed value table cannot be changed, the following method is only applicable to tables:

# l is a table, l2 is another table

l.extend(l2) Add all the elements of table l2 at the end of table l
l .append(x) Append x element to the end of l
l.sort() Sort the elements in l
l.reverse() Reverse the elements in l
l.pop() Return: the last element of table l , and delete the element
del l[i] in table l Delete the element

(These methods above all operate on the original table and will affect the original table instead of returning a new table. )

4. Here are some methods for strings

#str is a string, sub is a substring of str. s is a sequence, and its elements are all strings. width is an integer used to describe the width of the newly generated string.

str.count(sub) Returns: The number of times sub appears in str
str.find(sub) Returns: Starting from the left, find the position where sub appears for the first time in str. If str does not contain sub, return -1

str.index(sub) Return: Starting from the left, find the position where sub first appears in str. If str does not contain sub, raise an error

str.rfind(sub) Return: Starting from the right, find the position where sub first appears in str. If str does not contain sub, return -1

str.rindex(sub) Return: Starting from the right, find the position where sub first appears in str. If str does not contain sub, raise an error


str.isalnum() Returns: True, if all characters are letters or numbers
str.isalpha() Returns: True, if all characters are letters
str .isdigit() Returns: True, if all characters are numbers
str.istitle() Returns: True, if the first letters of all words are uppercase
str.isspace() Returns: True, if all characters are uppercase Is a space
str.islower() Returns: True, if all characters are lowercase letters
str.isupper() Returns: True, if all characters are uppercase letters

str.split([sep, [max] ]) Return: Starting from the left, using spaces as separators, split str into multiple substrings, max times in total. Return the resulting substring in a table. You can use commas or other separators in the form of str.split(',')

str.rsplit([sep, [max]]) Return: Starting from the right, using spaces as the separator, split str into Multiple substrings, split max times in total. Return the resulting substring in a table. You can use commas or other separators in the form of str.rsplit(',')

str.join(s) Return: Combine the elements in s into a string using str as the separator.

str.strip([sub]) Return: Remove the spaces at the beginning and end of the string. You can also provide the parameter sub to remove the sub at the beginning and end of the string

str.replace(sub, new_sub) Returns: Replace sub in str with a new string new_sub
str.capitalize() Returns: Capitalizes the first letter of str
str.lower() Returns: Changes all letters of str is lowercase
str.upper()                                                           using using using                     ‐ out’s off out off off ‐ ‐ back‐ ‐ return:                                                             off. Capitalize the first letter of the word (separated by spaces)

str.center(width) Returns: a string with length width, put the original string into the center of the string, and leave other empty positions as spaces.

str.ljust(width) Returns: a string with length width, put the original string into the string with left alignment, and leave other empty positions as spaces.

str.rjust(width) Returns: a string of length width. The original string is right-aligned and put into the string, and other empty positions are spaces.