Talking about the Python string

A python string is a sequence type in which an element is a character. Because sequence types are a data structure in which elements are placed sequentially, you can either get a character by index or specify an index range to get a set of characters.

>>> ch= ' ABCDE ' >>> print ("ch[0]=", Ch[0], "ch[-1]=", Ch[-1]) ch[0]= a ch[-1]= E

Index is an integer and cannot be crossed out from 0 to Lne (str)-1, otherwise an error occurs.

>>> len (CH) 5>>> Ch[5]traceback (most recent call last):  File "<pyshell#4>", line 1, in <mo Dule>    ch[5]indexerror:string index out of range

Reverse print string

def resstr (CH):    mid=len (CH) for    C in range (mid):        print (ch[mid-1-c],end= ") >>> resstr (' ABCDE ') Edcba

SB's preparation, reverse string, string cannot be modified. Error message: ' str ' object does not support item assignment

The Shard of a string is the separation of a part of a string from a given string, which can be indexed in the following form I,j,k
I is the starting position, J is the index end position, but does not include the string in the J position, the index number increments at each increment of K

>>> s= "Hello World" >>> print (S[0:len (s): 2]) hlowrd>>> print (S[1:len (s): 3],end= '---') Eood---

Indexed index, which is from 0 to Len (str)-1, can also use a negative index, ranging from-N to-1. The starting position of the negative index is the end of the string.

st= ' ASDFG ' Print (st[-1:0:-1]) Gfds

The index of the string shard, the starting position of the index I, the index end position J, and the step K can be omitted, omit I, starting from 0 or 1, omit J when the last string ends, omit the K time step is 1.

st= ' ASDFGHJK ' Print (St[:0:-1]) print (St[2::2]) print (st[0:5:]) KJHGFDSDGJASDFG

string-related operations, which can be used for connection operations, logical operations, and string handling functions.

st1= ' abc ' st2= "def" Print ("{0}+{1}={2}". Format (ST1,ST2,ST1+ST2)) print ("{0:s}*5={1}". Format (st1,st1*5)) abc+def= Abcdefabc*5=abcabcabcabcabc

Method of String
The string is immutable, and any string that changes the string will return a new string, and the Python string can be considered a class.

st1= ' AbcDEF ' Print ("{0:s}.upper () ={1:s}". Format (St1,st1.upper ())) print ("{0:s}.lower () ={1:s}". Format (ST1, St1.lower ())) print ("{0:s}.swapcase () ={1:s}". Format (St1,st1.swapcase ())) Abcdef.upper () =abcdefabcdef.lower () = Abcdefabcdef.swapcase () =abcdefst1= ' abcdefasde ' Print ("a count={0}". Format (St1.count (' a '))) print ("{0} start with {1}" is {2} ". Format (ST1, ' abc ', St1.startswith (' abc '))) print (" {0} End with {1} is {2} ". Format (st1, ' de ', st1.startswith (' de ') )) A count=2abcdefasde start with ABC was True ABCDEFASDE end with de is False st1= ' abcdefasde ' Print ("{0} Replace 123: {1}" . Format (St1,st1.replace (' abc ', ' 123 '))) print ("{0} remove {1} left char---{2}". Format (St1, ", St1.strip ())) Abcdefasde Replace 123:123defasde abcdefasde Remove left   char---abcdefasde

The method of string is too many, not say, no meaning.

Byte object
In Python, a sequence of non-immutable Unicode characters is called a string, unlike Byte and string. A sequence of strings that cannot be changed to encode between 0--255 is called a byte object.

By=b ' ABC & ' Print (Type (by)) print ("Length=", len) <class ' bytes ' >length= 5

You can define a byte object with a ' B ' in front of the string, each string can be an ASCII character, and you can use the Len () function to calculate the length of a byte object.

Ch=input (' Enter several numbers comma separated: ') d=ch.split (', ') print (d) sum=0for num in D:    sum+=float (num) print ("Ths sum=", sum) Enter several numbers comma separated: 2.2,3.3,5.5,6.8[' 2.2 ', ' 3.3 ', ' 5.5 ', ' 6.8 ']ths sum= 17.8

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