How to replace all None values with the string "Null" in a dictionary

[dcrespo]

Hi all,

How can I replace all None values with the string 'Null' in a
dictionary?

For example:
convert this:
a = {'item1': 45, 'item2': None}

into this:
a = {'item1': 45, 'item2': 'Null'}

Thanks

Daniel