Three-level menu.

. 1 MENU = {
 2      ' Beijing ' : {
 3          ' Haidian ' : {
 4              ' Wudaokou ' : {
 . 5                  ' SOHO ' : {},
 . 6                  ' YORK ' : {},
 . 7                  ' Google ' : {}
 . 8              },
 . 9              ' Zhongguancun ' : {
 10                  ' iQIYI ' : {},
 11                  ' car home ' : {},
 12                  ' All Time Youku ':{},
13              },
 14              ' on the ground ' : {
 15                  ' Baidu ' : {}
 16              }
 17          }
 18          ' Changping ' : {
 19              ' River ' : {
 20                  ' old boys ' : {},
 21                  ' Northern ' : {}
 22              }
 23              ' Tiantongyuan ' : {},
 24              ' huilongguan ' : {}
 25          }
 26          'Sunny' : {},
 27          ' East ' : {}
 28      }
 29      ' Shanghai ' : {
 30          ' minhang ' : {
 31              , " People's Square " : {
 32                  ' Fried Chicken ' : {}
 33              }
 34          }
 35          ' Zhabei ' : {
 36              ' station ' : {
 37                  ' Cheng ' : {}
 38              }
 39          },
40         'Pudong ' : {}
 41      }
 42      ' Shandong ' : {}
 43  }
 44 is  
45  ' '' 
46  1 may be sequentially selected for each sub-menu to enter the variables do dictionary # 2, for circulating Key
 47  2. from recede back layer of any layer selected INPUT #
 48  3 # can exit the program from any one exits the loop
 49  '' ' 
50  
51 is c_menu = MENU    # current dictionary current = C 
52 is p_menu = []     # by list storing the dictionary information, Previous P = 
53 is  the while True:
 54 is      # cycles dictionary list print Key 
55      for Key in c_menu:
 56 is         Print (Key)
 57 is      Choice = INPUT ( " >>>: " ). .strip () Lower ()   # waits for user input to remove all lower rear space to facilitate identification 
58      IF Choice in c_menu:    # the next level 
59          p_menu.append (c_menu)   # add to the list of the current layer 
60          c_menu = c_menu [choice]     # current layer becomes the choice of selecting the next layer 
61 is      elif choice == " B " :
 62 is          IF p_menu:
 63 is              c_menu p_menu = [-1] # taken from the list to the last value, i.e., the circulating level, assigned to current_menu 
64             p_menu.pop ()    # After deleting, keeping a list of error does not return to the upper   
 65      elif Choice == " q " : BREAK   # If you enter q, the program ends. 
66      the else :
 67          Print ( ' error message, please choose again ' .center (50, ' * ' ))
 68      IF  not c_menu:
 69          Print ( ' there is no information, press B to return: ' )
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