Conditional statement: If ... else elif
Loop statement: while for
Exit: Break continue return exit pass
Application Scenario: Level Three menu Enter City serial number enter the menu input b return input Q exit
#!/usr/bin/env Python3ImportOSImportSYS" "make a level three menu Shandong Rizhao East Haven Lanshan Wulian" "defShowcd (dir):" ":p Aram dir: The directory to go: return: Returns the list under the directory to go" " if(Os.path.exists (dir)): Dirlist=os.listdir (dir) Num= 1 forDirNameinchdirlist:Print("%s.%s"%(num, dirname)) Num+ = 1Print("Please enter B to return or Q to exit") returnDirlistdir=os.getcwd () dirlist=showcd (dir) while(True): City=input ("Please enter:") if(city=="Q"): Exit (0)elif(city=="b"): Dir=os.path.dirname (dir) dirlist=showcd (dir)elif(Os.listdir (dir+"/"+dirlist[int (city)-1]): dir=dir+"/"+dirlist[int (city)-1] Dirlist=showcd (dir)Else: Print("There are no subordinate cities")
Python conditional statements and loops