Python dictionary replace values

Each Answer to this Q is separated by one/two green lines.

I have a dictionary with 20 000 plus entries with at the moment simply the unique word and the number of times the word was used in the source text (Dante’s Divine Comedy in Italian).

I would like to work through all entries replacing the value with an actual definition as I find them. Is there a simple way to iterate through the keywords that have as a value a number in order to replace (as I research the meaning)?

The dictionary starts:

{'corse': 378, 'cielo,': 209, 'mute;': 16, 'torre,': 11, 'corsa': 53, 'assessin': 21, 'corso': 417, 'Tolomea': 21}  # etc.

Sort of an application that will suggest a keyword to research and define.

via dict.update() function

In case you need a declarative solution, you can use dict.update() to change values in a dict.

Either like this:

my_dict.update({'key1': 'value1', 'key2': 'value2'})

or like this:

my_dict.update(key1='value1', key2='value2')

via dictionary unpacking

Since Python 3.5 you can also use dictionary unpacking for this:

my_dict = { **my_dict, 'key1': 'value1', 'key2': 'value2'}

Note: This creates a new dictionary.

via merge operator or update operator

Since Python 3.9 you can also use the merge operator on dictionaries:

my_dict = my_dict | {'key1': 'value1', 'key2': 'value2'}

Note: This creates a new dictionary.

Or you can use the update operator:

my_dict |= {'key1': 'value1', 'key2': 'value2'}

You cannot select on specific values (or types of values). You’d either make a reverse index (map numbers back to (lists of) keys) or you have to loop through all values every time.

If you are processing numbers in arbitrary order anyway, you may as well loop through all items:

for key, value in inputdict.items():
    # do something with value
    inputdict[key] = newvalue

otherwise I’d go with the reverse index:

from collections import defaultdict

reverse = defaultdict(list)
for key, value in inputdict.items():
    reverse[value].append(key)

Now you can look up keys by value:

for key in reverse[value]:
    inputdict[key] = newvalue

If you iterate over a dictionary you get the keys, so assuming your dictionary is in a variable called data and you have some function find_definition() which gets the definition, you can do something like the following:

for word in data:
    data[word] = find_definition(word)

I think this may help you solve your issue.

Imagine you have a dictionary like this:

dic0 = {0:"CL1", 1:"CL2", 2:"CL3"}

And you want to change values by this one:

dic0to1 = {"CL1":"Unknown1", "CL2":"Unknown2", "CL3":"Unknown3"}

You can use code bellow to change values of dic0 properly respected to dic0to1 without worrying yourself about indexes in dictionary:

for x, y in dic0.items():
    dic0[x] = dic0to1[y]

Now you have:

>>> dic0
{0: 'Unknown1', 1: 'Unknown2', 2: 'Unknown3'}

Just had to do something similar. My approach for sanitizing data for python based on Sadra Sabouri’s answer:

def sanitize(value):
    if str(value) == 'false':
        return False
    elif str(value) == 'true':
        return True
    elif str(value) == 'null':
        return None
    return value

for k,v in some_dict.items():
        some_dict[k] = sanitize(v)

data = {key1: value1, key2: value2, key3: value3}

for key in data:
   if key == key1:
       data[key1] = change
       print(data)

this will replace key1: value1 to key1: change


The answers/resolutions are collected from stackoverflow, are licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0 .