将列表与字典值进行比较

Question

I am supposed to be comparing a sentence to a set of keys:values and swapping certain words in the sentence with the corresponding values in the dictionary pairs. Here is what I have so far:

keys = input().split(" ")
sentence = input().split(" ")
parent = {}
g = 0
for x in range(len(keys)):
    if x % 2:
        parent[first] = keys[x]
    else:
        first = keys[x]

for k,f in enumerate(sentence):
    if f is parent.keys():
        sentence[k] = parent.get(f,na)
    else:
        g+=1
print(sentence)
print(g)

The print statements in the bottom are just confirming the second loop is running. There are few other things I need to tidy up, but my main problem now is

for k,f in enumerate(sentence):
    if f is parent.keys():
        sentence[k] = parent.get(f,na)

The first if keeps getting skipped over and I get my print(g) to output the number of loops it did; which is all of them.

Thanks!!

Answer 1

As others have said in comments you have a typo. if f is parent.keys(): should be if f in parent.keys(): or more succinctly if f in parent:

The reason for this error is that parent.keys() produces a list of keys, and you're attempting to check whether f is the same object as the keys of the dictionary. What you were probably trying to do was check whether the string f existed within the list of keys.

For future reference x is y checks whether x and y refer to the same object. x in y checks whether the value of x is present in the sequence y.