Python data type-string common operations

This time, we mainly introduce the methods and examples of string common operation

1.python string

To declare a string in Python, there are usually three ways to add a single quotation mark, double quotation mark, or triple quotation mark on either side of it, as follows:

' Hello '  " " ' Hello shang hai haha '

Once the string in Python is declared, it cannot be changed, as follows:

# The string is an immutable variable, that is, you cannot change the content by re-assigning a value to a location ' Hello '  'k'# by subscript to modify the value of the string, error message: TypeError: ' str ' object does not support Item Assignment

Python string is a common built-in method for manipulating strings, as follows:

In method:

# in method: Determine whether the content exists in the string '  'print('hello' in name)   #  Determine if hello exists in name, execution result is trueprint('in# determine if Shanghai exists in name, execution result is false

Not method:

Name ='Hello bei Jing Zao an' #Defining Strings#Not method: Returns the ' opposite value ' of an expression result. Returns false if the expression result is truePrint('Hello'  not inchName#Judging Hello does not exist in name, execution result is falsePrint('ABC'  not inchName#To determine that ABC does not exist in name, the execution result is true

Is method:

# is to determine if the memory address is the same ' xiaoming '  'xiaoming'print is b)  #A and B are the same values, Memory, point to the same memory address, point to the result is trueprint(ID (a))print(ID (b))  # The memory address of the variable can be viewed by this method of ID (variable name)

The string value operation method is as follows:

' Hello bei jing one day ' Print (Names[0:10])  # 1. Can be evaluated by subscript, Slice, gu head does not contain tail, the execution result is: Hello bei  for inch names:     Print (name)      # 2. With a For loop value, loop through each element of the Loop object (names)  for inch Range (len (names)):     Print (Names[k])  # 3. The length of the loop names, and the value of K is the number, which is equivalent to the subscript of the string

EndsWith, Isalnum, Isalpha Methods for strings:

 name =  " hello World was world   " print  (Name.endswith ( d   ')  #   to determine whether to end with U, execute the result as a Boolean, working example: You can tell if the picture ends in JPG  print  ( " ab123  "  . Isalnum ()) #   Determines whether the input string contains numbers and letters, determines whether the password contains numbers and letters, Can be used to return a result to a Boolean  print  ( " abcda   ". Isalpha ()) #   

Determines whether the input string is a number, as follows:

' abcdERF123 ' Print ('123'. IsDigit ())  # determines whether the input string is a number, and returns the result as a Boolean value

Remove the whitespace from the string, as follows:

#Remove SpacesPrint('AB FS'. Lstrip ())#by default, the left space and line wrapping of the string are removed, and the result: AB FSPrint('Hello'. Rstrip ())#The default is to remove the whitespace and line breaks to the right of the string and execute the result: HelloPrint('\nmysql ABCD'. Strip ())#The default is to remove both sides of the space and line, the result: MySQL ABCD, the middle of the space can not be removedPrint('Mysqlmy'. Strip ('m'))#removes the specified string, for example: Remove the M element on both sides, and execute the result: Ysqlm y

The Join method of the string, as follows:

#join is used to stitch each element of an iterative object through a string--->join (can iterate over object parameter types)Print('*'. Join (name))#concatenate each element in the string with the * sign, executing the result: a*b*c*d*e*r*f*1*2*3, returning a new variable valuePrint('Use the * number after stitching the name value:', name)#the contents of the name string have not been changed, the result of the execution: abcdERF123Nums = ['YBQ','Lhl','LSH']Print(','. Join (Nums))#converts the list to a string, using a comma connection between each element, and executes the result: Ybq,lhl,lsh#another way to convert a list to a string#nums = [' Ybq ', ' lhl ', ' LSH ']#temp = '#For i in Nums:#temp = temp+i+ ', ' #列表转换为字符串, coercion type conversion, execution result is: Ybq,lhl,lsh#Print (Temp.strip (', '))

Replace the Replace string, as follows:

' MySQL is db mysql MySQL ' Print (St.replace ('mysql'oracle'))    # replace MySQL in a string with Oracle Print (St.replace ('mysql'oracle', 1))   # You can enter the number of times you want to replace a replacement element when there are more

Look for the Find string, as follows:

Name ='Hello World was world'Print(Name.find (' World'))#find the index of a stringPrint(Name.find (' World', 3, 10))#You can specify the range of the lookup string, 3,15 is the start, end subscript value, and the subscript value Gu Tou regardless of the tailPrint(Name.find ('XXX'))#The returned result is 1 when the found string does not existPrint(Name.rfind (' World'))#find the string and look it up from the back and execute the result:

Cut the string spilt, return the result type to list, as follows:

# to cut a string, the returned type is List ' Zcl,py,zyz,ywq '  # cut the string into listname1_list = Name1.split (',')  # to divide the string by commas, The return result for the value of list,name1 does not change the print(name1_list)     # execution result to the list type: [' zcl ', ' py ', ' zyz ', ' Ywq ']print(Name1.split ())  # splits a string by a space, returns a list with only one element, executes the result: [' Zcl,py,zyz, Ywq ']
Print (name1.spilt (' \ n '))  #按照换行符分割字符串

Splitting a string by line break is not commonly used, as follows:

Print ('1+2+3\n1+3+4'. Splitlines ())   # split by line break, splitting the contents of each line of the file as an element of the list, executing the result: [' 1+2+3 ', ' 1+3+4 ']

The string randomly generates uppercase and lowercase letters, numbers, and uses the following:

Import   stringprint(string.ascii_letters + string.digits)  # output all uppercase and lowercase letters + (0-9) digits Print (string.ascii_letters)   # output case of the English alphabet, execution result: abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz Print # Output lowercase English letter, execution result: abcdefghijklmnopqrstuvwxyz Print (string.ascii_uppercase)  # Output lowercase English letter, execution result: abcdefghijklmnopqrstuvwxyz

format string, as follows:

Print (The Name.format (name='byz'# formatted string displays print(Name.format_map ({ ' name ' ' Zhangsan ' '  Age ' # Formatting Dictionaries

Methods that are not commonly used in strings, you can understand:

The judgment and conversion of uppercase and lowercase letters in a string are as follows:

Name ='abcdERF123'Print('AA'. Islower ())#determines whether the input string is a lowercase letter, and returns the result as a Boolean valuePrint('ASD'. Isupper ())#determines whether the input string is an uppercase letterPrint(Name.lower ())#turns the uppercase letters in a string into lowercase, executing the result: abcderf123Print(Name.upper ())#capitalize the lowercase letters in the string to execute the result: ABCDERF123Print('ABCdef'. Swapcase ())#uppercase and lowercase letters reversed, execution result: AbcDEF

The mapping of strings can be used for password encryption, as follows:

#Mappingp = Str.maketrans ('ABCDEFG','1234567')#The preceding string and the following string are mapped, a-->1,c-->3Print('Ccaegg'. Translate (p))#The output is mapped to the above Maketrans string, and the result is: 331577#Anti-Solution mappingNew_p = Str.translate ('1234567','ABCDEFG')Print('Ccaegg'. Translate (new_p))#The output is mapped to the above Maketrans string, and the result is: Ccaegg

Capitalize the first letter of a string

' Hello World was world ' Print (Name.capitalize ())  # capitalize first letter, execution result: Hello World Print ' * ' # With a total length of 50, the value of the name string is placed in the middle, and both sides complement the * number display

Welcome to Daniel to supplement ~ ~ ~

Python data type-string common operations