Lowercase both keys and values in a Python Dictionary

Question

I have a dictionary I would like to insert into a mongodb. The code works but I would like to insert it with both keys AND values moved to lowercase for ease of searching later. Some example data would be:

{'Publisher': u'TSR', 'Language': u'en', 'Title': u'The Silent Blade', 'Authors': [u'R. A. Salvatore'], 'ISBN-13': u'9780786913886', 'Year': u'1998'} {'Publisher': u'Houghton Mifflin Harcourt', 'Language': u'en', 'Title': u'A Field Guide To Mushrooms, North America', 'Authors': [u'Kent H. McKnight', u'Roger Tory Peterson', u'Vera B. McKnight'], 'ISBN-13': u'9780395910900', 'Year': u'1998'}

Notice the second option has multiple authors, so a list in the dictionary. I am still new to python and this has kept me up many nights. Can't seem to get my head wrapped around how to access them. I can change the case of the key case with this

book_data = {k.lower(): v for k, v in book_data.items()} #keys book_data = {v.lower(): k for k, v in book_data.items()} #values

But I have tried to mod this from keys to values and just put them back to back, but it fails on the list in second example. What is the best way to iterate over the entire dictionary and lowercase the keys as values? Most of my searches just return changing the case of the keys.

Mureinik · Accepted Answer · 2017-05-28 16:42:49Z

I'd define a function to recursively lowercase a value, and then use it in a dict comprehension:

import types def lowerValues(arg): # Handle iterables if hasattr(arg, "__iter__"): return [lowerValues(item) for item in arg] elif isinstance(arg, types.StringTypes): return arg.lower() else: return arg book_data = {k.lower() : lowerValues(v) for k,v in book_data.items()}

Mario Valadez Trevino · Accepted Answer · 2019-05-15 15:58:35Z

1

Do the whole thing in one step:

book_data = {k.lower(): str(v).lower() for k, v in dict.items()}

edited May 15, 2019 at 15:58

answered May 14, 2019 at 10:38

Mario Valadez Trevino

392 bronze badges

2 Comments

sanyassh Over a year ago

Your solution will fail on examples provided in the question.

Mario Valadez Trevino Over a year ago

You are right Sanyash, I forgot to add the str() first. I tried in both now and it works.

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