Subtract 1 from all values in dictionary

Question

I have a dictionary like the following:

dict = {'hi':1, 'hi2':2, 'lskdjf':3}

It continues like this for over a million values.

I want to convert this into a dictionary with a value starting at 0

For example, this is the desired output:

dict = {'hi':0, 'hi2':1, 'lskdjf':2}

How can this be done efficiently?

Answer 1

You can either iterate over the dictionary to update it...

for k in dict_:
    dict_[k] -= 1

... or create a new dictionary with a dictionary comprehension.

new_dict = {k: v - 1 for k, v in dict_.items()}

In both cases note that I replaced your variable name by dict_ to avoid overwriting the built-in dict name.