Hello, I'm little F.
String is the basic data type in Python, and it is used in almost every Python program.
Today, little F will take you to learn the 31 most important built-in string methods.
I hope you can find helpful skills from it.
▍1,Slicing
slicing slice, which extracts some elements (such as specific range, index and split value) from the list or tuple according to certain conditions
s = ' hello ' s = s[:] print(s) # hello s = ' hello ' s = s[3:8] print(s) # hello
▍2,strip()
The strip() method is used to remove the specified character (space or newline by default) or character sequence at the beginning and end of the string.
s = ' hello '.strip() print(s) # hello s = '###hello###'.strip() print(s) # ###hello###
When using the strip() method, spaces or line breaks are removed by default, so the # sign is not removed.
You can add the specified character to the strip() method, as shown below.
s = '###hello###'.strip('#')
print(s)
# helloIn addition, when the specified content is not at the beginning and end, it will not be removed.
s = ' \n \t hello\n'.strip('\n')
print(s)
#
# hello
s = '\n \t hello\n'.strip('\n')
print(s)
# helloThe first \ n is preceded by a space, so only the trailing newline character will be taken.
Finally, the parameter of strip() method is to strip all combinations of its values. You can see the following case.
s = 'www.baidu.com'.strip('cmow.')
print(s)
# baiduThe outermost first and last character parameter values are stripped from the string. The character is removed from the front end until it reaches a string character that is not included in the character set.
A similar action occurs at the tail.
▍3,lstrip()
Removes the specified character (space or newline by default) or character sequence to the left of the string.
s = ' hello '.lstrip() print(s) # hello
Similarly, you can remove all strings contained in the character set on the left.
s = 'Arthur: three!'.lstrip('Arthur: ')
print(s)
# ee!▍4,rstrip()
Removes the specified character (space or newline by default) or character sequence to the right of the string.
s = ' hello '.rstrip() print(s) # hello
▍5,removeprefix()
Python3.9 to remove the prefix.
# python 3.9
s = 'Arthur: three!'.removeprefix('Arthur: ')
print(s)
# three!Compared with strip(), strings in character set are not matched one by one.
▍6,removesuffix()
Python3.9 to remove the suffix.
s = 'HelloPython'.removesuffix('Python')
print(s)
# Hello▍7,replace()
Replace the content in the specified string with the content in the specified string.
s = 'string methods in python'.replace(' ', '-')
print(s)
# string-methods-in-python
s = 'string methods in python'.replace(' ', '')
print(s)
# stringmethodsinpython▍8,re.sub()
re is a regular expression, and sub is substitute, indicating substitution.
re.sub is the replacement of relatively complex points.
import re
s = "string methods in python"
s2 = s.replace(' ', '-')
print(s2)
# string----methods-in-python
s = "string methods in python"
s2 = re.sub("\s+", "-", s)
print(s2)
# string-methods-in-pythonCompare with replace() and use re Sub() performs the replacement operation, which is indeed more advanced.
▍9,split()
The string is separated, and the final result is a list.
s = 'string methods in python'.split() print(s) # ['string', 'methods', 'in', 'python']
When no separator is specified, it is separated by spaces by default.
s = 'string methods in python'.split(',')
print(s)
# ['string methods in python']In addition, you can specify the number of times the string is separated.
s = 'string methods in python'.split(' ', maxsplit=1)
print(s)
# ['string', 'methods in python']▍10,rsplit()
Separate strings from the right.
s = 'string methods in python'.rsplit(' ', maxsplit=1)
print(s)
# ['string methods in', 'python']▍11,join()
string.join(seq). Take string as the separator to combine all elements (string representation) in SEQ into a new string.
list_of_strings = ['string', 'methods', 'in', 'python'] s = '-'.join(list_of_strings) print(s) # string-methods-in-python list_of_strings = ['string', 'methods', 'in', 'python'] s = ' '.join(list_of_strings) print(s) # string methods in python
▍12,upper()
Convert all letters in the string to uppercase.
s = 'simple is better than complex'.upper() print(s) # SIMPLE IS BETTER THAN COMPLEX
▍13,lower()
Converts all letters in the string to lowercase.
s = 'SIMPLE IS BETTER THAN COMPLEX'.lower() print(s) # simple is better than complex
▍14,capitalize()
Converts the first letter in a string to uppercase.
s = 'simple is better than complex'.capitalize() print(s) # Simple is better than complex
▍15,islower()
Judge whether all letters in the string are lowercase. If yes, it returns True; otherwise, it returns False.
print('SIMPLE IS BETTER THAN COMPLEX'.islower()) # False
print('simple is better than complex'.islower()) # True▍16,isupper()
Judge whether all letters in the string are capitalized. If yes, it returns True; otherwise, it returns False.
print('SIMPLE IS BETTER THAN COMPLEX'.isupper()) # True
print('SIMPLE IS BETTER THAN complex'.isupper()) # False▍17,isalpha()
Returns True if the string has at least one character and all characters are letters, otherwise returns False.
s = 'python' print(s.isalpha()) # True s = '123' print(s.isalpha()) # False s = 'python123' print(s.isalpha()) # False s = 'python-123' print(s.isalpha()) # False
▍18,isnumeric()
Returns True if the string contains only numeric characters, otherwise False.
s = 'python' print(s.isnumeric()) # False s = '123' print(s.isnumeric()) # True s = 'python123' print(s.isnumeric()) # False s = 'python-123' print(s.isnumeric()) # False
▍19,isalnum()
Returns True if there is at least one character in the string and all characters are letters or numbers, otherwise returns False.
s = 'python' print(s.isalnum()) # True s = '123' print(s.isalnum()) # True s = 'python123' print(s.isalnum()) # True s = 'python-123' print(s.isalnum()) # False
▍20,count()
Returns the number of times the specified content appears in the string.
n = 'hello world'.count('o')
print(n)
# 2
n = 'hello world'.count('oo')
print(n)
# 0▍21,find()
Detect whether the specified content is included in the string. If so, return the starting index value; otherwise, return - 1.
s = 'Machine Learning'
idx = s.find('a')
print(idx)
print(s[idx:])
# 1
# achine Learning
s = 'Machine Learning'
idx = s.find('aa')
print(idx)
print(s[idx:])
# -1
# gIn addition, you can specify the starting range.
s = 'Machine Learning'
idx = s.find('a', 2)
print(idx)
print(s[idx:])
# 10
# arning▍22,rfind()
Similar to the find() function, it returns the position of the last occurrence of the string. If there is no match, it returns - 1.
s = 'Machine Learning'
idx = s.rfind('a')
print(idx)
print(s[idx:])
# 10
# arning▍23,startswith()
Check whether the string starts with the specified content. If yes, it returns True; otherwise, it returns False.
print('Patrick'.startswith('P'))
# True▍24,endswith()
Check whether the string ends with the specified content. If yes, it returns True; otherwise, it returns False.
print('Patrick'.endswith('ck'))
# True▍25,partition()
string.partition(str) is a bit like a combination of find() and split().
From the first position where STR appears, the string is divided into a 3-element tuple (string_pre_str,str,string_post_str). If STR is not included in the string, the string_pre_str==string.
s = 'Python is awesome!'
parts = s.partition('is')
print(parts)
# ('Python ', 'is', ' awesome!')
s = 'Python is awesome!'
parts = s.partition('was')
print(parts)
# ('Python is awesome!', '', '')▍26,center()
Returns a new string centered on the original string and filled with spaces to the length width.
s = 'Python is awesome!' s = s.center(30, '-') print(s) # ------Python is awesome!------
▍27,ljust()
Returns a new string that is left aligned with the original string and filled with spaces to the length width.
s = 'Python is awesome!' s = s.ljust(30, '-') print(s) # Python is awesome!------------
▍28,rjust()
Returns a new string with the original string right justified and filled with spaces to the length width.
s = 'Python is awesome!' s = s.rjust(30, '-') print(s) # ------------Python is awesome!
▍29,f-Strings
f-string is a new syntax for formatting strings.
Compared with other formatting methods, they are not only easier to read, simpler, less error prone, but also faster!
num = 1
language = 'Python'
s = f'{language} is the number {num} in programming!'
print(s)
# Python is the number 1 in programming!
num = 1
language = 'Python'
s = f'{language} is the number {num*8} in programming!'
print(s)
# Python is the number 8 in programming!▍30,swapcase()
Flips the case of letters in a string.
s = 'HELLO world' s = s.swapcase() print(s) # hello WORLD
▍31,zfill()
string.zfill(width).
Returns a string with a length of width. The original string is aligned to the right and filled with 0 in front.
s = '42'.zfill(5) print(s) # 00042 s = '-42'.zfill(5) print(s) # -0042 s = '+42'.zfill(5) print(s) # +0042