Python string function

• Convert letters to lowercase ：lower()

>>> "Smith".lower()
'smith'

• upper()

>>> "abcd".upper()
'ABCD'

• find() function ： Find the substring position

>>> 'hello world'.find('el')
1

find The function has three arguments , The last two parameters are the starting position of the search

>>> 'hello world'.find('el')
1
>>> 'hello world'.find('o')
4
>>> 'hello world'.find('o',5)
7

• replace() function ： Replace

>>> 'hello world'.replace(' ','_')
'hello_world'
>>> 'hello world'.replace('','_')
'_h_e_l_l_o_ _w_o_r_l_d_'

• strip() function ： Remove the space on both sides
• lstrip(): Remove the leftmost space
• rstrip(): Remove the rightmost space

>>> s=" Ni Hao "
>>> s.strip()
'Ni Hao'
>>> s.lstrip()
'Ni Hao '
>>> s.rstrip()
' Ni Hao'