str='hello world'
str.startswith('he')
str.endswith{'y"}
str.expendtabs()
st='he llo world'
st.expandtabs(tabsize=10)
st.find('e') :find first element and return index value
st.format(0） ： formatting string assignment element for value
usage: for example :st='hello kitty {'name'}' st.format(name='alan')
st='hello world {name} is {age}'
st.format(name='alan',age=30)
st.format_map({})
st.index('h')
st.isalnum() ；include alphabet and number ,contain alphabet and digit
st.isdecimal(): judage one string whether a decimal digit
st.isdigit() judage element whether number integery
st.isnumeric() judage element whether numeric
'afs123'.isidentifier() judage element whether alphabet
'aa'.islower()
'AAA'.isupper()
' '=.isspace()
'My sister.istitle() first alphabet capital
'My siste.lower() all alphabet lower case
'my sister.upper() all alphabet capital
'my sister.swapcase() twist alphabet capital or lower case
'my.sister'.ljust
'my sister'.strip() .delete front or rear space,line break
st.lstrip()
st.rstrip()
st.replace('a','b')
st.rfind('t')
st.lfind('t')
st.split(‘ ’）：for example 'hello kitty'.split('i') hello k i tty
st.rsplit('i',1)
st.title(). first capital