31个必备的Python字符串方法，建议收藏！

s = ' hello '
s = s[:]
print(s)
#hello
s = ' hello '
s = s[3:8]
print(s)
# hello

s = ' hello '.strip()
print(s)
# hello
s = '###hello###'.strip()
print(s)
# ###hello###

s = '###hello###'.strip('#')
print(s)
# hello

s = ' n t hellon'.strip('n')
print(s)
#
#hello
s = 'n t hellon'.strip('n')
print(s)
#hello

s = 'www.baidu.com'.strip('cmow.')
print(s)
# baidu

s = ' hello '.lstrip()
print(s)
# hello

s = 'Arthur: three!'.lstrip('Arthur: ')
print(s)
# ee!

s = ' hello '.rstrip()
print(s)
#hello

# python 3.9
s = 'Arthur: three!'.removeprefix('Arthur: ')
print(s)
# three!

s = 'HelloPython'.removesuffix('Python')
print(s)
# Hello

s = 'string methods in python'.replace(' ', '-')
print(s)
# string-methods-in-python
s = 'string methods in python'.replace(' ', '')
print(s)
# stringmethodsinpython

import re
s = "stringmethods in python"
s2 = s.replace(' ', '-')
print(s2)
# string----methods-in-python
s = "stringmethods in python"
s2 = re.sub("s+", "-", s)
print(s2)
# string-methods-in-python

s = 'string methods in python'.split()
print(s)
# ['string', 'methods', 'in', 'python']

s = 'string methods in python'.split(',')
print(s)
# ['string methods in python']

s = 'string methods in python'.split(' ', maxsplit=1)
print(s)
# ['string', 'methods in python']

s = 'string methods in python'.rsplit(' ', maxsplit=1)
print(s)
# ['string methods in', 'python']

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

s = 'simple is better than complex'.upper()
print(s)
# SIMPLE IS BETTER THAN COMPLEX

s = 'SIMPLE IS BETTER THAN COMPLEX'.lower()
print(s)
# simple is better than complex

s = 'simple is better than complex'.capitalize()
print(s)
# Simple is better than complex

print('SIMPLE IS BETTER THAN COMPLEX'.islower()) # False
print('simple is better than complex'.islower()) # True

print('SIMPLE IS BETTER THAN COMPLEX'.isupper()) # True
print('SIMPLE IS BETTER THAN complex'.isupper()) # 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

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

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

n = 'hello world'.count('o')
print(n)
# 2
n = 'hello world'.count('oo')
print(n)
# 0

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
# g

s = 'Machine Learning'
idx = s.find('a', 2)
print(idx)
print(s[idx:])
# 10
# arning

s = 'Machine Learning'
idx = s.rfind('a')
print(idx)
print(s[idx:])
# 10
# arning

print('Patrick'.startswith('P'))
# True

print('Patrick'.endswith('ck'))
# True

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!', '', '')

s = 'Python is awesome!'
s = s.center(30, '-')
print(s)
# ------Python is awesome!------

s = 'Python is awesome!'
s = s.ljust(30, '-')
print(s)
# Python is awesome!------------

s = 'Python is awesome!'
s = s.rjust(30, '-')
print(s)
# ------------Python is awesome!

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!

s = 'HELLO world'
s = s.swapcase()
print(s)
# hello WORLD

s = '42'.zfill(5)
print(s)
# 00042
s = '-42'.zfill(5)
print(s)
# -0042
s = '+42'.zfill(5)
print(s)
# +0042