[Tutor] Dictionaries

Martin A. Brown martin at linux-ip.net
Sun Jun 17 16:50:20 CEST 2012


 : I am having a problem with a small application I am writing. I 
 : have to have the user input the key, then have the program output 
 : the value associated with it. A way to inform the user that the 
 : key they entered is not in the dictionary or somefing would be 
 : nice also.

I would agree also with Emile--in the future, you will probably get 
a better answer if you are more specific in your question.  This one 
is a pretty easy question to answer and show you some samples for 
how to approach this with code snippets.

I will assume that userinput is a variable with the contents of 
interest that your user typed.  I will use the variable d to 
represent some dictionary (any dictionary).

  if userinput in d:
      print 'Found', userinput, 'in dictionary, value was', d[userinput]
      print 'No entry'

Depending on what else you are doing (besides printing), you might 
also look into the get() method of dictionaries:

  default = '<nonexistent>'
  string_to_print = d.get(userinput,default)
  print 'You typed %s.  The entry was %s.' % ( userinput, string_to_print)

These are pretty common usage patterns for dictionaries, so you 
might benefit from looking at the other sorts of things that you can 
do with dictionaries.

Good luck,


Martin A. Brown

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