Re-learn Python, learn python

Re-learn Python, learn python
Application of while statement

 

Example:

1 "2 Statement: the user can log on to the system at most three times 3 after the third failure, the program ends 4 5" 6 user_table = {"python ": "important", "java": "more_important", "shell ": "linux"} 7 time = 1 8 9 while time <4:10 user_name = input ("Enter your Username:") 11 user_password = input ("enter your password: ") 12 if user_name in user_table.keys () and user_password in user_table.values (): # very low, because the user name and password can be mixed, update it later 13 print (" welcome, master !! ") 14 break15 else: 16 print (" you failed login system !! ") 17 if time = :18 print (" Three chances are all userd !! ") 19 time + = 1

PS: 1. The running result is not displayed.

2. The ide I selected is Pycharm, and the registration code is my Baidu Keyword: pycharm 2017 registration code (I can use it by myself, but do not use it in regular companies)

 

 

 

Understanding and examples of continue and break statements

 

Continue: the current cycle jumps out and continues the next cycle

Break: jumps out of the current cycle

1 flag = False 2 for I in range (10): 3 if I <6: 4 continue #0 to 5 is skipped, the subsequent print statement cannot execute 5 print (I) # When I = 6, print 6 for j in range (10): 7 print (j) 8 if j = 5: 9 flag = True10 break # interrupts the current loop, and the second for loop is interrupted 11 # if flag: 12 # if break cancels the comments of the two rows, the first for loop is interrupted and can be determined based on the format.

 

 

 

Python classic data type-list)

Example:

1 list1 = ["a", "B", "c", "e", "f", "d"] 2 3 print (list1 [3]) # The first index is the index value starting from left or right by default. The following index example is also 4 print (list1 [1:]). # The first value to the last value 5 print (list1 [1:-1]) #-1 is the last and second value 6 print (list1 [:-1]) # The list is reversed. -1 indicates 7 print (list1 [4:-1]) from right to left 8 print (list1) 9 10 11 # list Modification 12 list1.append ("python ") 13 print (list1) 14 15 # modify the value of the specified position 16 list1 [2] = "java" 17 print (list1) 18 19 # insert 20 list1.insert (1, "ruby ") 21 print (list1) 22 23 # Delete method remove del pop24 list1.remove ("java") # You can also use the index to specify the value, list1.remove (list [1]) 25 print (list1) 26 list1.pop (2) 27 print (list1) 28 del list1 [1] 29 print (list1)

Running result:

E ['B', 'C', 'E', 'F', 'D'] ['B', 'C', 'E ', 'F'] ['D', 'F', 'E', 'C', 'B', 'a'] ['F', 'E ', 'C', 'B', 'a'] ['A', 'B', 'C', 'E', 'F ', 'D'] ['A', 'B', 'C', 'E', 'E', 'F', 'D', 'python'] ['A ', 'B', 'java', 'E', 'F', 'D', 'python'] ['A', 'ruby', 'B ', 'java', 'E', 'F', 'D', 'python'] ['A', 'Ruby ',' B ', 'E ', 'F', 'D', 'python'] ['A', 'Ruby ', 'E', 'F', 'D ', 'python'] ['A', 'E', 'F', 'D', 'python'] The process has ended. Exit code 0.

 

PS: the built-in functions of the list are put in tomorrow's notes