Python Quick Tutorial (Supplement 01): Python Sequence Method

The following built-in functions 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 True

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 the 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: x is the first in s The subscript that appears

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

# l is a table, l2 is another table

l.extend(l2) in table l Add all elements of table l2 at the end

l.append(x)                                        . l.pop()                                                                                                                                                                         using using   to use   to                 through ’ ’ s ’ s ’ through ’ s ‐                .                                                                Affects the original table instead of returning a new table )

Here are some methods for strings. Although strings are a special type of constant value table, the string class has methods that mutate strings. The essence of these methods is not to operate on the original string, but to delete the original string and create a new string, so it does not conflict with the characteristics of the fixed value table.

#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, an error occurs.

str.rfind(sub) Returns: 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() Return: True, if all characters are letters or numbers

str.isalpha() Return: 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 spaces

str.islower() Returns: True, if all characters are lowercase letters

str.isupper() Returns: True, if all characters are uppercase letters

str .split([sep, [max]]) Returns: 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 the sub in str with a new string new_sub

str.capitalize() Returns: Replace str The first letter is capitalized

str.lower() Returns: Change all letters of str to lowercase

str.upper()                                                               using ‐             ‐                           use using ’ ’ s ’ s ’ s ‐   ‐ ‐                             out out out out out through out through out using through out through out out through out out through out's'' ’ ‐ ‐ ‐ ‐‐ ‐‐‐‐ together's to ? Capitalize the first letter of the word (separated by spaces)

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

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