Python: Check if a key in a dictionary is containe

Question

Assuming I've a dictionary,

mydict = { "short bread": "bread", 
           "black bread": "bread", 
           "banana cake": "cake", 
           "wheat bread": "bread" }

Given the string "wheat bread breakfast today" I want to check if any key in my dictionary is contained in the string. If so, I want to return the value in the dictionary associated with that key.

I want to use a list comprehension for this.

Here's what I have so far.

mykeys = mydict.keys()
mystring = "wheat breads breakfast today"
if any(s in string for s in mykeys):
    print("Yes")

This outputs Yes as expected. What I really want to do is to use the s variable to index into mydict. But s has a limited scope inside the any() function. So the following does not work.

if any(s in mystring for s in mykeys):
    print(mydict[s])

Any workaround? Many thanks!

Answer 1

Just loop through the keys and check each one.

for key in mydict:
    if key in mystring:
         print(mydict[key])

If you want to do it in a list comprehension, just check the key on each iteration.

[val for key,val in mydict.items() if key in mystring]

You could also filter the dictionary keys in the initial loop instead of a separate check.

for key in (key in mydict if key in mystring):
    print(mydict[key])

Or you could use filter if you feel like getting functional with it.

list(map(mydict.get, filter(lambda x:x in mystring, mydict)))

Or another way with filter (don't actually use this one, it's super unreadable and just here for fun).

list(filter(bool,[v*(k in mystring) for k,v in mydict.items()]))

Answer 2

mydict = { "short bread": "bread", 
           "black bread": "bread", 
           "banana cake": "cake", 
           "wheat bread": "bread" }

s = "wheat bread breakfast today"

for key in mydict:
    if key in s:
        print mydict[key]