Python string commonly used encyclopedia

String related operations:

+ :string1+string2 #Connect strings, link the next string to the back of the previous string

* :string*n #Create a new string and repeat the original string n times

[] :string[n] #Get a character at the corresponding position from the string

[:] :string[n:m] #Intercept the string, if it is: m from beginning to m, if it is n: from n to end

in :char in string #Judge whether a character is in the string, if it returns true (True)

not in :char not in string #Judge whether a character is not in the string, if it returns true (True)

r/R : r/Rstring #The actual meaning of escaped characters is prohibited, the entire character is the original meaning

Conversion of character case in the string:

* S.lower() #Lowercase
* S.upper( ) #Capital
* S.swapcase() #Case swap
* S.capitalize() #Capitalize the first letter
* String.capwords(S) #This is a method in the module. It separates S using the split() function, then uses capitalize() to change the first letter to uppercase, and finally uses join() to merge it together
* S.title() #Only the first letter is uppercase, and the rest are lowercase, which is not available in the module This method

aligns the string when outputting:

* S.ljust(width,[fillchar]) #Output width characters, S is left-aligned, and the missing part is filled with fillchar. The default is spaces.
* S.rjust(width,[fillchar]) #Align right
* S.center(width, [fillchar]) #Align center
* S.zfill(width) #Change S to width and align to the right , fill the missing part with 0

Search and replace in the string:

* S.find(substr, [start, [end]]) #Return the label of the first letter of substr appearing in S, if If there is no substr, -1 is returned. The function of start and end is equivalent to searching in S[start:end]
* S.index(substr, [start, [end]]) #Same as find(), except that when there is no substr in S, one will be returned Runtime error
* S.rfind(substr, [start, [end]]) #Returns the label of the first letter of the substr that last appeared in S. If there is no substr in S, it returns -1, that is, from the right The first letter number of substr that appears for the first time
* S.rindex(substr, [start, [end]])
* S.count(substr, [start, [end]]) #Calculate substr in S The number of occurrences in
* S.replace(oldstr, newstr, [count]) #Replace oldstar in S with newstr, and count is the number of replacements. This is the general form of replacement. There are also some functions to replace special characters
* S.strip([chars]) #Remove all the characters in the chars before and after S. It can be understood as replacing the chars before and after S with None
* S.lstrip([chars])
* S.rstrip([chars])
* S.expandtabs([tabsize]) #Replace the tab characters in S without spaces, and replace each tab with tabsize spaces, default It is the division and combination of 8

strings:

* S.split([sep, [maxsplit]]) #Use sep as the separator to divide S into a list. maxsplit represents the number of splits. The default separator is a blank character
* S.rsplit([sep, [maxsplit]])
* S.splitlines([keepends]) #Divide S into a list according to the line separator, keepends is a bool value, if If true, line separators will be preserved after each line.
* S.join(seq) #Connect the sequence represented by seq, the string sequence, with S.

String mapping. This function includes two functions:

* String.maketrans(from, to) #Return a translation table composed of 256 characters, in which the characters in from are converted into to in one-to-one correspondence, so from and to must be equal lengths.
* S.translate(table[,deletechars]) #Use the translation table of the above function to translate S and delete some characters in deletechars. It should be noted that if S is a unicode string, the deletechars parameter is not supported, and the same function can be achieved by translating a certain character into None. In addition, you can use the functions of the codecs module to create more powerful translation tables.

Strings also have a pair of encoding and decoding functions:

* S.encode([encoding,[errors]]) #The encoding can have multiple values, such as gb2312 gbk gb18030 bz2 zlib big5 bzse64, etc. are supported. The default value of errors is "strict", which means UnicodeError. Possible values ​​are 'ignore', 'replace', 'xmlcharrefreplace', 'backslashreplace' and all values ​​registered via codecs.register_error. This part involves the codecs module, which is not particularly clear
* S.decode([encoding,[errors]])

The test function of the string, the function returns all bool values:

* S.startwith(prefix[, start[,end]]) #Whether it starts with prefix
* S.endwith(suffix[,start[,end]]) #Ends with suffix
* S.isalnum() #Whether it is all letters and numbers, and has at least A character
* S.isalpha() # Whether it is all letters and at least one character
* S.isdigit() # Whether it is all numbers and at least one character
* S.isspace() # Whether it is all blank characters, and there is at least one character
* S.islower() # Whether the letters in S are all lowercase
* S.isupper() # Whether the letters in S are uppercase
* S.istitle() # Whether S is Capitalized

String type conversion functions, these functions are in the string module:

* string.atoi(s[,base]) #base defaults to 10, if it is 0, then s can be in the form of 012 or 0x23 string, if it is 16, then s can only be a string in the form of 0x23 or 0X12
* string.atol(s[,base]) #Convert to long
* string.atof(s[,base]) #convert to float