Python basic data type--str

First, the creation of a string

Test = str ()/"" "Test = str (" Licheng ")/" Licheng "

• No arguments, creating an empty string
• A parameter that creates a normal string
• two parameters, int (bytes, encoded)

Second, the common method of the string

#capitalize (): string first character uppercase String = ' This is a string. ' New_str = String.capitalize () print (NEW_STR) #输出: This is a string. #center (width, fillchar=none): Place the string in the middle, and at the specified length, fill in string = ' This is a string with the specified character. ' New_str = String.center (+, ' * ') print (NEW_STR) #输出: ******this is a string.******* #count (sub, Start=none, End=none) : Computes the number of characters in a string = ' This is a string '. New_str = String.count (' i ') print (NEW_STR) #输出: 3 #decode/encode (Encoding=none, Errors=none): decode/decode string = ' This is a String. ' New_str = String.decode () New_str = String.encode () print (NEW_STR) #endswith (self, suffix, start=none, end=none) : Determines whether to end a character string = ' This is a string. ' New_str = String.endswith (' ing. ') Print (NEW_STR) #输出: True #find (self, sub, Start=none, End=none): Finds the position of the specified character in a string = ' This is a string '. New_str = String.find (' a ') #找的到的情况print (NEW_STR) #输出: 8new_str = String.find (' xx ') #找不到的情况返回 -1print (NEW_STR) #输出:-1 # Index (self, sub, Start=none, End=none): similar to findstring = ' This is a string. ' New_str = String.index (' a ') #找的到的情况print (NEW_STR) #输Out: 8new_str = String.index (' xx ') #找不到的情况, program error print (NEW_STR) #输出: program operation error, valueerror:substring not found #isalnum (self) : Determines whether the string is all numbers and letters, or returns TRUE if it is, otherwise returns falsestring = ' My name is yue,my 18. ' New_str = String.isalnum () print (NEW_STR) #输出: falsestring = ' Haha18121314lala ' new_str = String.isalnum () print (NEW_STR) #输出: True #isalpha (self): Determines whether the string is all letters, or returns TRUE if it is, otherwise falsestring = ' ABCDEFG ' new_str = String.isalpha () print (NEW_STR) #输出: truestring = ' My name is yue ' new_str = String.isalpha () #字母中间带空格, no special characters print (NEW_STR) #输出: False # isdigit (self) : Determines whether the string is a number, or returns True if it is, otherwise returns falsestring = ' 1234567890 ' new_str = String.isdigit () print (NEW_STR) #输出: truestring = ' Haha123lala ' new_str = String.isdigit () #中间带空格, no special characters print (NEW_STR) #输出: False # islower (self): Determines whether the letters in a string are lowercase, Returns true if it is, otherwise returns falsestring = ' My name is Yue,my 18. ' New_str = String.islower () print (NEW_STR) #输出: truestring = ' My name is Yue,my ' 18. ' New_str = String.islower () print (NEW_STR) #输出: False # Isupper (self): detects whether all letters in the string are uppercase. string = ' MY NAME is YUE. ' New_str = String.isupper () print (NEW_STR) #输出: truestring = ' My name is Yue. ' New_str = String.isupper () print (NEW_STR) #输出: False # join (self, iterable): Generates a new string for the element in the sequence with the specified character connection. String = ("haha", "lala", "Ohoh") str = "-" Print (Str.join (string)) #输出: Haha-lala-ohoh # lower (self): Converts all uppercase characters in a string to lowercase. String = "My Name is YUE." Print (String.Lower ()) # output: My name is Yue. # Lstrip (self, chars=none): Truncates the left space of the string or specifies the character. String = "My Name is YUE." Print (String.lstrip ()) #输出: My name is yue.string = "My name is YUE." Print (String.lstrip (' My)) #输出: Name is YUE. #replace (self, old, new, Count=none): replaces the older string in the string with the new one, and if you specify the third parameter max, the replacement does not exceed Max times. string = "My name is Yue." Print (String.Replace ("Yue", "Ying")) #输出: My name is Ying. # RFind (self, sub, Start=none, End=none): Returns the position of the last occurrence of the string, or 1 if there is no match. string = "My name is Yue." Print (String.rfind (' is ')) #输出: 8string = "My name is Yue." Print (String.rfind (' XXX ')) #输出: -1 # split (self, Sep=none, Maxsplit=none): Slices The string by specifying a delimiter. string = "haha lala gege" Print (string. Split (")) #输出: [' haha ', ' lala ', ' Gege ']print (String.Split (', 1)) #输出: [' haha ', ' lala Gege '] # rsplit (self, sep=none, MA Xsplit=none): Slices the string from right by specifying a delimiter. string = "haha lala gege" Print (String.rsplit (")) #输出: [' haha ', ' lala ', ' Gege ']print (String.rsplit (", 1)) #输出: [' Haha lal A ', ' Gege '] # Rstrip (self, chars=none): Deletes the specified character at the end of the string (the default is a space). String = "My name is Yue." Print (String.rstrip ()) #输出: My name is Yue. # strip (Self, chars=none): Removes the character specified by the tail of the string (the default is a space). string = "My name is Yue." Print (String.strip ()) #输出: My name is Yue. # upper (self): Converts lowercase letters in a string to uppercase. string = "My name is Yue,my 18." Print (String.upper ()) #输出: MY NAME is yue,my 18.

Str source Three, the public function of the string

• Index (only one element can be taken)
• Slices (take multiple elements)
• Length (len)
  • Python2: Length by byte
  • Python3: Count length by character
• For loop (version Loop unit of the same length)

Iv. conversion of characters to bytes

# convert GBK encoded characters to bytes s = "Li Cheng" b = bytes (s, encoding= "GBK") type (b)  output to byte type # converts bytes to characters C = str (b, encoding= "GBK")

Five, string formatting

There are two ways to format a Python string: a percent-semicolon, format-mode

The percent of the semicolon is relatively old, and format is a more advanced way to replace the old way, the two coexist.

1, percent of the way

%[(name)][flags][width]. [Precision]typecode

Detailed parameters

Common formatting:

TPL = "I am%s"% "spark" TPL = "I am%s age%d"% ("spark", +) TPL = "I am% (name) s age percent (age) d"% {"name": "Spark", "AG E ":" TPL = "percent%.2f"% 99.97623 TPL = "I am% (PP)." 2f "% {" pp ": 123.425556,} TPL =" I am%.2f percent "% {" pp ": 123.425 556,}

2. Format mode

[[Fill]align] [Sign] [#] [0] [Width] [,] [. Precision] [Type]

Detailed parameters

Common formatting:

 1 TPL = "I am {}, age {}, {}". Format ("Seven", +, ' Alex ') 2 3 TPL = "I am {}, age {}, {}". Format (*["Seven", "Alex" ]) 4 5 TPL = "I am {0}, age {1}, really {0}". Format ("seven", +) 6 7 TPL = "I am {0}, age {1}, really {0}". Format (*[  "Seven") 8 9 TPL = "I am {name}, age {age}, really {name}". Format (name= "Seven", age=18), TPL = "I am {name}", Age {Age}, really {name} '. Format (**{"name": "Seven", "Age": +}), TPL = "I am {0[0]}, age {0[1]}, really {0[2]}". fo Rmat ([1, 2, 3], [One, one, and all]) (= "I am {: s}, age {:d}," ". Format (" Seven ",, 88888.1) AM {: s}, age {:d} ". Format (*[" Seven ", [+]):" I am {name:s}, age {age:d} ". Format (name=" Seven ", AGE=18) TP L = "I am {name:s}, age {age:d}". Format (**{"name": "Seven", "Age": ()) = "Numbers: {: b},{:o},{:d},{:x},{:x}, {: %} ". Format (15.87623, 2, 15, +, +), TPL =" numbers: {: b},{:o},{:d},{:x},{:x}, {:%} ". Format (15,, 15, 15, 1 5, 15.87623, 2) TPL = "numbers: {0:b},{0:o},{0:d},{0:x},{0:x}, {0:%}". Format (page), TPL = "Numbers: {num:b},{num:o},{num:d},{num:x},{ Num:x}, {num:%} ". Format (NUM=15)

More formatting operations: https://docs.python.org/3/library/string.html

Python basic data type--str