Question

I am writing a function that takes in an argument. From that argument, I want to compare it to a dictionary’s set of keys and return the key’s value for any matches. So far I have been able to only return the argument matches for the keys.

def func(str):
  a = []
  b = {'a':'b','c':'d','e':'f'}
  for i in str:
    if i in b.keys():
      a.append(i)
  return a

Output sample:

func(‘abcdefghiabcdefghi’)

[‘a’,’c’,’e’,’a’,’c’,’e’]

Wanted output:

[‘b’,’d’,’f’,’b’,’d’,’f’]

Answer 1

Best not to use str as a variable name. I think your function can be written more simply like this

def func(mystr):
  b = {'a':'b','c':'d','e':'f'}
  return [b[k] for k in mystr if k in b]

If you don’t want to use a list comprehension, then you can fix it like this

def func(mystr):
  a = []
  b = {'a':'b','c':'d','e':'f'}
  for i in mystr:
    if i in b:           # i in b works the same as i in b.keys()
      a.append(b[i])     # look up the key(i) in the dictionary(b) here
  return a