check if numeric element is in an interval key dictionary in python

from the following dictionary with tuple as keys and a string as value:

dict_interval = {(1,5):"foo",(5,100):"bar"}

by using the dict, how would be possible to use a function with the following behaviour?

age = 4    
categorizer(age, dict_interval)

gives the following output:

"foo"

Answer

If you expect age to be within multiple intervals and you want to get them all:

# Categoriser, returns a list
def categoriser(age, d) -> list:
    return [value for key, value in d.items() 
            if is_between(age, key)]

# Helper function
def is_between(value, interval):
    return interval[0] <= value < interval[1]

I have added an overlapping interval to your data

>>> dict_interval = {(1,5): "foo", (2, 5): "foo2", (5,100): "bar"}
>>> categoriser(4, dict_interval)
["foo", "foo2"]

If you want the first value only:

# Categoriser, returns first value 
def categoriser(age, d) -> str:
    for key, value in d.items():
        if is_between(age, key):
            return value

>>> categoriser(4, dict_interval)
"foo"