python , input number, output letter

Question

I want to convert a number into a letter, if the user enters .8, the program would output a B if the user inputs a .7, the program prints a C, I am not sure how to do it?

a = 0.9 
b = 0.8
c = 0.7 
d = 0.6 
f = 0.5 

number = float(raw_input('enter number: '))

i = 0
for i in (a, b ,c ,d, f):
       if number == i:
          print i


   ''' Dictionarys,  not sure how to use them, would it work best for this purpose? '''

   ''' I am getting an error '''
'''{ a: '0.9' b: '0.8'  c: '0.7' d :'0.6' f: '0.5'}'''

'''
  File "<stdin>", line 1
    { a: '0.9' b: '0.8'  c: '0.7' d :'0.6' f: '0.5'}
               ^
SyntaxError: invalid syntax
''' 

Answer 1

You want to map from the numbers to the letters, so you want the numbers to be keys in the dictionary:

number = float(raw_input('enter number: '))

my_map = { 0.9: "a", 0.8:"b", 0.7: "c", 0.6:"d", 0.5:"e"}
print my_map[number]

Answer 2

Just because sometime looks like a number/float, doesn't always mean you need to convert it to one. In your case it's easy to use strings. (The handling of invalid input is a little simpler)

>>> D = {'0.9': 'a', '0.8': 'b', '0.7': 'c', '0.6': 'd', '0.5': 'f'}
>>> number = raw_input('enter number: ')
enter number: 0.8
>>> print D[number]
b

Aside. Comparing floats for equality can cause interesting bugs. In your case it would be ok, but you need to be careful if you were calculating a number, say by adding results together

>>> 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 == 0.1 * 9
False

Answer 3

you can use integer as a key ,also I recommend use Get() method of dictionary to get a default value if no such key exsits

The easiest way it is

number = float(raw_input('enter number: '))
d = {0.9:"a",0.8:"b",0.7:"c",0.6:"d",0.5:"f"}
print d.get(number,"other")