Python learning path 3: python learning path

Python learning path 3: python learning path
Content of this section:

• Common string processing.
• Format the output string.
• String replacement.
• Conversion of strings and binary data.
• Dictionary operations

String operation

Common string processing

Name = 'vector 'print (name. capitalize () # print (name. count ('E') # determine the number of print (name. center (50, '-') # print 50 characters in total, place the vector in the middle, and fill print (name. endswith ('R') # judge the end of a string. If it ends with r, trueprint (name. expandtabs (tabsize = 10) # If \ t is added to the string, add the tabsize space print (name. find ('EC') # locate the position of e in the string print (name. isalnum () # returns Trueprint (name. isalpha () # returns Trueprint (name. isdecimal () # If the string is a decimal number, Trueprint (name. isdigit () # returns Trueprint (name. isidentifier () # returns Trueprint (name. islower () # determines whether it is in lowercase. If yes, Trueprint (name. isupper () # determines whether it is in upper case. If yes, Trueprint (name. isspace () # determines whether it Is a space. If yes, Trueprint ('My Name Is 'Is returned '. istitle () # determines whether it is the title (uppercase). If yes, Trueprint ('+' is returned '. join (['1', '2', '3']) # Splice each element in the list with '+' to print (name. ljust (50, "*") # If the string length is less than 50, use * to supplement print (name. must ust (50, "*") # If the string length is less than 50, use * to supplement print (name. lower () # converts uppercase to lowercase print (name. upper () # converts lowercase letters to uppercase print ('\ nvector '. lstrip () # Remove the space on the left of the string and press ENTER print ('vector \ n '. rstrip () # Remove the spaces on the right of the string and press ENTER print ('\ nvector \ n '. strip () # Remove the spaces on both sides of the string and press ENTER print ('name is a Book '. rfind ('A') # Find a from the right and return the position print ('name is a Book '. split ('') # splits the string into a list by space. If no parameter is specified, the default Delimiter is space print ('name is \ na Book '. splitlines () # load the string into a list print ('name is a Book' Based on the linefeed '. swapcase () # case-insensitive print ('name is a Book '. title () # change the string to the title (uppercase) print ('name '. zfill (50) # If there are less than 50 strings, fill the string with 0 on the left.

Format outputString

Name = 'vector {name} {age} 'print (name. format (name = 'Rev ', age = 123) # format the string print (name. format_map ({'name': 'Rev ', 'age': 123}) # format a string in dictionary format

String replacement

# Use maketrans to set the replacement rule, and then use translate to replace p = str. maketrans ('asdfgn ', '000000') # The first parameter is the replaced character, and the second parameter is the replaced character print ('name '. translate (p) # input the rule p and print it out as 61me, because n and a are replaced by print ('name') by 6 and 1 '. replace ('n', 'B', 1) # replace n with B. The third parameter indicates the number of replicas. If n is not specified, all replicas are replaced by default.

Conversion of strings and binary data

Msg = 'I love the Yanbian daily empire' print (msg) # string output print (msg. encode (encoding = 'utf-8') # convert the string to binary print (msg. encode (encoding = 'utf-8 '). decode (encoding = 'utf-8') # convert binary data to a string

The encode parameter indicates the format before and the decode parameter indicates the format to convert. If encode and decode do not write parameters, the default value is UTF-8.

 

Dictionary

A dictionary is a key-value data type. It is used to query the details of a corresponding page through strokes and letters.

Dictionary features:

• Dict is unordered
• The key must be unique and so must be de-duplicated.

Syntax:

info = {    'str1':'zhangsan',    'str2':'lisi',    'str3':'wangwu',    'str4':'zhaoliu'}

 

Common dictionary operations:

Info = {'str1': 'hangsan', 'str2': 'lisi', 'str3': 'hangzhou', 'str4': 'zhaoliu'} print (info) # print all dictionaries print (info ['str2']) # print the dictionary element info ['str1'] = 'yangzirui 'based on the key name # The value will be modified, if the key name does not exist, del info ['str2'] # Delete the element info. pop ('str2') # This also deletes print (info. popitem () # delete a random key and return its key-Value Pair print (info ['str1']) # print the data. If the key name does not exist, an error is returned, print (info. get ('str2') # print data. If the key name does not exist, none is returned. print ('str1' in info) is recommended. # Check whether the key name exists and print true, otherwise print falseaaa = info. setdefault ('str5', 'liangsohohfefho') # If the key in info is str5, the corresponding value is directly returned. If no, then, the corresponding value a = {'str1': 'asdfsdfs',} info is returned. update (a) # merge dictionary a into info. If there is a cross, use the value info in Dictionary. items () # converts a dictionary to a list. Each element in the list is composed of tuples, and each key-value pair of the original dictionary forms a c = dict. fromkeys ([, 3], 'test') # create a new dictionary with a key of 1, 2, 3 and a value of test. If no value is written, the values are none; the values assigned later are shared by the three keys, so all the values are changed when you change them.

 

Loop dictionary:

Info = {'str1': 'hangsan ', 'str2': 'lisi', 'str3': 'hangww', 'str4 ': 'zhaoliu'} # first loop method for I in info: print (I, info [I]) # this should be the most basic loop # second loop method for k, v in info. items (): print (k, v) # The efficiency of this loop method is not as high as that of the first loop because the dictionary needs to be converted to a list.

Output result: (this is true for both cycles)