Returning values from dictionary in python

Question

switch = {(0,21): 'never have a pension',
          (21,50): 'might have a pension',
          (50,65): 'definitely have a pension',
          (65, 200): 'already collecting pension'}
for key, value in switch:
  a=input()
  if key[0] < a< key[1]:
        print(value)

when I try to execute the program it raise an error

TypeError: 'int' object is not subscriptable.

I don't know how to fix. please help

Answer 1

When you do for kev, value in switch , you're not getting the tuple and the string - you're getting the two values from the tuple. This is because iterating over a dictionary by default iterates over its keys.

Instead, you want to do for key, value in switch.items() .

Answer 2

I suppose you would like to do:

while True:
    try:
        a = int(input())
    except ValueError:
        print('not an int, try again')


for k, v in switch.items():
    if k[0] < a < k[1]:
        print(v)

And depending your needs:

>>> [v for k, v in switch.items() if k[0] < a < k[1]]
['might have a pension']

Answer 3

By the way, this is a fairly unpythonic way to do a multi-range test.

Consider this if-elif tree instead:

a = input()

if a < 21:
    msg = 'never have a pension'
elif a < 50:
    msg = 'might have a pension'
elif a < 65:
    msg = 'definitely have a pension'
else:
    msg = 'already collecting pension'

print msg

Advantages: it is simpler to understand, avoids duplicating the endpoints (which are most likely to change), works even if people somehow manage to live past 200, and actually avoids a bug in your original code (where people would already be collecting a pension if they were exactly 21).

Disadvantages: code is longer, and msg and a are repeated. However, this is offset by the fact that you can now implement more customizable and appropriate logic under each case.