如何在Python中更新字典值，让用户选择要更新的密钥，然后选择新值？

Question

I am trying to write a program where my brother and I can enter and edit information from our football game rosters to compare teams and manage players, etc. This is my first 'big' project i've tried.

I have a nested dictionary inside a dictionary, I'm able to get the user to create the dictionaries etc. But when i try to have the 'user' (via raw_input) go back to edit them I get stuck. Below i tried to put a simplified version of the code down of what i think is relevant to my error. If I need to put down a full version let me know.

player1 = {'stat1' : A, 'stat2' : 2, 'stat3' : 3} #existing players are the dictionaries 
player2 = {'stat1' : A, 'stat2' : 2, 'stat3' : 3} # containing the name of stat and its value
position1 = {'player1' : player1} # in each position the string (name of player) is the key and
position2 = {'player2' : player2} # the similarly named dict containing the statisics is the value
position = raw_input('which position? ') # user chooses which position to edit
if position == 'position1':
  print position1 # shows user what players are available to choose from in that position
  player = raw_input('which player? ') #user chooses player from available at that position
  if player == player1:
    print player # shows user the current stats for the player they chose
    edit_query = raw_input('Do you need to edit one or more of these stats? ')
    editloop = 0
    while editloop < 1: # while loop to allow multiple stats editing
      if edit_query == 'yes': 
        stat_to_edit = raw_input('Which stat? (If you are done type "done") ')
          if stat_to_edit == 'done': #end while loop for stat editing
            editloop = editloop +1
          else:
            new_value = raw_input('new_value: ') #user inserts new value

# up to here everything is working. 
# in the following line, player should give the name of the
# dictionary to change (either player1 or player2) 
# stat_to_edit should give the key where the matching value is to be changed
# and new_value should update the stastic
# however I get TypeError 'str' object does not support item assignment

            player[stat_to_edit] = new_value #update statistic
      else:  # end loop if no stat editing is wanted
        fooedit = fooedit + 1

of course when i say "should give..." etc I mean to say "I want it to give.."

In summary I want the user to choose the player to edit, choose the stat to edit, then choose the new value

Answer 1

The problems seems that after this line

player = raw_input('which player? ')

the player will be the string, containing what the user have typed in, and not the dictionary, like player1 . This explains, why Python fails to assign to its part. You can instead write like this:

player = raw_input('which player? ')
if player == 'player1': # these are strings!
  current_player = player1 # this is dictionary!
  ....
  current_player[...] = ... # change the dictionary

Also note, that the Python assignment to a name typically does no copy object, but only adds another name for the same existing object. Consider this example (from Python console):

>>> a = {'1': 1}
>>> a
{'1': 1}
>>> b = a
>>> b
{'1': 1}
>>> b['1'] = 2
>>> b
{'1': 2}
>>> a
{'1': 2}
>>>