Python basics, including lists, tuples, dictionaries, strings, set sets, while loops, for loops, operators.

     1.continue: Jumping out of a loop, making the next loop      2.break jumping out of the loop      3. Constant (all uppercase) NAME = CJK   Generally changed the third-party libraries that will make mistakes      4.python, and then install and import them first. Install module: PIP command For example: Pip install pandas     5.os.system (command) on Linux and window line      6.res  = os.popen (' ipconfig '). Read ()     &NBSP;7.PYC is a thing.       8.sys.exit () jump out of all       9, list: name =  [' Minglong ', ' Minghu ', ' + ', ' Jack ']  & nbsp     Name[0]   is   ' Minglong '  name[-1]   is ' Jack ' name[:2] is from the beginning to the Minghu never get the Last, Name[2:] From 32 to the most After     Modify element: name[0] = ' Wangminglong '  name[0][0]   is ' m ', take out one of the values in the element     insert: Name.insert (2, ', Minggou ') is added minggou    append to Minghu: Name.append (' xiaoming ') added xiaoming    Delete at the end: Name.remove (' Xiaoming ') directly delete xiaoming or  del  name[0:2] will be the first to the second delete, Name.pop (0) Delete the first number and return this element.    step: name[::2] Step is 2, take one element at a intervals     check: 32 in the name to determine if the second nAme list    name.count (' Minglong '): Lookup for Name list has several ' Minglong ' returns of 1.    name.index (' Minglong '); Find the index of Minglong, and return 0. If more than one Minglong returns the index of the first found result.    name2 = [' CJK ', ' Xiaoqiang ',2,4]   name.extend (name2): Append name2 to the name list     Name.reverse (): Sorts the elements in turn.    name.cope () shallow copy. There is a deepcopy in the import copy module which is a deep copy. The difference is that if a list is nested, the list in the nested lists will be changed with the original list, while the deep copy is a complete clone of the list, and the 2 are independent of each other.    len (name): The length of the list, here is the number of elements.  7.26   10, tuple: Name = (1, ' qqq ', ')   read-only list.       Name.count and Name.index on 2 apps.           11. String:      Remove blank strip:name = input (' username: '), if name.strip () = = ' Cao ': print (' Welcome ') defaults to remove whitespace characters (including ' \ n ', ' \ R ',   ' \ t ',   ').     Split split:names = ' Cao, Cjk,alex '   name2 = Names.split (', ') then name2 = [' Cao ', ' CJK ', ' Alex '] splits the string into lists as ', '.      join The elements in the list into a string: Name3 = ' | '. Join (name2) Name3 = ' Cao|cjk|alex '       Determine if there are spaces: name = ' Cao Fa ', print (' in name ')   return true     str.format (): msg = ' Hello {name} ' it ' s been {time] days since I saw you ' MSG2 = Msg.format (name = ' CJK ', time = 30) or msg = ' Hello {0} dddd{1} ' MSG2 = Msg.format (' Alex ', 33) is also OK. Dic1 = {' name ': ' Alex ', ' age ': +   MSG2 = Msg.format (**dic1) or list1 = [' Alex ', ' +]   MSG2 = Msg.format (*list1) is passed All the elements in the List1.            String indexes are the same as slices and lists: name = ' Caofajia ' name[0] = ' C '       Str.center (): As name = ' Cao ', Name.center (40, '-') generates '--------Cao--------' A total of 40 characters centered on the CAO and complete with '-'. &NBSP;12, operators      12.1, arithmetic operators                +      -       *       /      //     %        **     12.2, relational operators           &NBsp;  <       <=      >        >=      ==     !=     12.3, Logical operators              and     or       not     12.4, bitwise operators              Inverse (~), Bitwise AND (&), or (|) and XOR (^) and left (<<) and right Shift (>>)      12.5   Assignment and increment assignment operators:              +=     -=      *=& nbsp;    /=     %=      **=              <<=     >>=      &=      ^=      |=&NBSP;&NBsp;      12.6  Supplement:            Plural cannot use relational operators       &NBSP ; The     bitwise operator can only be used for integer type 13. Dead Loop:          while true:print (' Nihao ') 14. Dictionary: id_db = {     12: {            ' name ': ' Cao ', ' Age ': ' addr ': ' Shandong '          },& nbsp    13:{            ' name ': ' Alex ', ' age ': one, ' addr ': ' Dongbei '       & nbsp  }}         : id_db[12] The value corresponding to key 12 is {' name ': ' Cao ', ' Age ': ' addr ': ' Shandong '}          change: id_db[12][' name ' = ' CJK ' Here changes ' Cao ' to ' CJK '         ' Delete: Id-db[12].pop (' addr ') delete the addr corresponding key value.         add: id_db[13][' qq_of_wife ' = 2134, added ' qq_of_wife:2134.     id_ ' in the dictionary below 13 Db.get (): The advantage is that if the key does not exist, return directly to none.     id_db.update (): Dict1 = {       13:{' name ': ' Shanpao ', ' age ':13           }       14:{' name ': ' Dashanpao ', ' age ' :21           }} if Id_db.update (Dict1)   id_db will change to add 14 and Dict1 13 covers id_db in 13.&N Bsp      id_db.items (): Generally not used in large-scale dictionaries, because it is inefficient to convert dictionaries into list forms.        id_db.values (): Displays a list of values.        id_db.keys (): Displays a list of key components.       Judgment key is not in the dictionary: db_db returns True.       Id_db.setdefault () and Id_db.fromkeys () are not generally used ...       Loop: for K, V in Id_db.items (): This is inefficient because you want to dict the list.                 for key in id_db:     general Use this.                          print (Key,id_db[key])   &NBS P  15. Set: unordered, non-repeating collection of sequences.             Presentation method: 1. S1 = {11,22,33} 2. Set ([11,22,33]) is also OK, actually executes a for loop to generate {11,22,33}.         &NBSP   Add Add:s1.add (44) Adds an element that is not in the set. If you repeat, do not add.             Clear and copy with list.           &NBSP;DIFFERENCE:S2 = {22,33,44} then s1.difference (S2) indicates that S1 exists in S2 and does not exist, generating a new object {11}.            symmetric_ difference:s1.symmetric_difference (S2) generate new {11,44}    & nbsp      difference_update:s1.difference_update (S2) changes the S1 to {11}. As long as there is an update in the back, the previous object S1 updated.             Remove: 1.dicard  s1.dicard (11) Remove 11,s1.dicard (11221) elements that do not exist do not error.                      2.remove  s1.remove (1123130) remove non-existent error &NB Sp                    3. Pop ()  s1.pop () randomly removes and generates a removed object, generally s3 = S1.pop ().             intersection:s1.intersection (S2) to intersect the object {22,33} that generated the row.             Union:  s1.union (S2)       &NBSp     Bulk Add: S1.update ([111,222,333,444]) update accepts objects that can be iterated, such as List,str,tuple.

Python basics, including lists, tuples, dictionaries, strings, set sets, while loops, for loops, operators.