New column in pandas dataframe from dictionary with lists as values

I have a dataframe:

df = pd.DataFrame({'col1': [111, 333, 456]})

And I have a dictionary with keys that correspond to a category and values with the type list.

dct = {'A': [111, 222, 333, 444], 'B': [123, 456, 789]}

The values in the list may or may not be found in col1. I’d like to create col2 that would return the key from dct.

My desired output is this:

col1   |   col2
-------+---------
111    |    A
333    |    A
456    |    B

I’ve tried df['col2'] = df['col1'].map(dct) but this returns NaN values.

>Solution :

You can try with:

df['col2'] = df['col1'].map(lambda x: [key for key in dct if x in dct[key]][0])

Returning:

   col1 col2
0   111    A
1   333    A
2   456    B