String common functions:
declare a variable
str="Hello World"
find() detects whether a string is contained, returns the position of the string, and -1 if it is not contained.
("Hello") # Return value: 0
("W") # Return value: 6, Note that a space is also a character, and there is a space before W, so the W position is 6.
("R") # return value：-1，is not included in theHello Worldcenter，If it does not contain return-1
index() detects whether the string contains the specified character and returns the beginning of the index value; if it does not, an error is reported.
("Hello") # Return value: 0
("o") # Return value: 4
("W") # Return value: 6
("R") # return value：error message (computing) ，on account ofRIt's not included.。 So it's advisable to use it with caution，If the value doesn't exist, the program is screwed.。
len() Returns the length of the string, counting from 0.
len(str) #Return value: 10
count() collects the number of times the specified character appears in the string
("o") return value：2, ocharacters in theHello WorldThere are two。
# You can also specify that the count() function starts at a certain position. The syntax is: count(" ",start,end)
('o',5,10) return value：1, rationale：Specifying a location will result in a change from the index5Start searching，indexing by10close。 5until (a time)10There is only one'o'
('o',4,len(str)) return value： 2，Indexing from4commencement，until (a time)字符串close。len(str)String length
replace() replaces the string
('hello','HELLO') # Replace lowercase hello with uppercase HELLO
('W','B') # particle marking the following noun as a direct objectWReplace withB
split() String split
('o') # Returns ["hell", "w", "rld"] as a list, with the o's inside hello world cut off.
upper() converts all characters to upper case
() # Return value is HELLO WORLD
title() converts initials to uppercase
() #Return value: Hello World
center() returns a new string with the original string centered and padded with spaces to the width of the length.
(80) #Return value: ( Hello World ) whose string is padded at both ends with spaces
join() constructs a new string by inserting a specified character after the string.
_str="_" list=["I","Love","You"] _str.join(list) # return value： I_Love_You An underscore is inserted after each list element.
isspace() detects whether the string contains only spaces, if so return Trun return False, in layman's terms is to determine the non-null verification
str=" " strOne="Good morning!" () # Return trun #come (or go) backfalse
isalnum() Detects if the password contains only numbers or letters. Usage: can be used to determine the password, in general the password can not enter Chinese characters or spaces.
strOne="a123" strTwo="a 456" () # Return trun () # come (or go) backfalse ，Because it contains spaces
isdigit() detects if a character contains only digits, returning Trun and False.
str='123' strone='a123' () come (or go) backtrun () come (or go) backfalse
isalpha() detects if a string contains only letters.
str="abcd" strone="123abacd" () # Return trun () # Returns false
summarize
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