I need to get a user to enter a sentence for an assignment. Using a `for` loop, I then need to replace all spaces with `%20` in order to prep the string to be used as a URL. I cannot for the life of me figure it out.

```
sentence = str(input("Please enter sentence:"))
space = (" ")

for space in sentence:
    space.replace(sentence, space, "%20", 500)
print(sentence)

```

This is what I have entered so far but it is completely wrong.