How do I use mapping of dictionary for value correction?

Question

I have a pandas series whose unique values are something like:

['toyota', 'toyouta', 'vokswagen', 'volkswagen,' 'vw', 'volvo']

Now I want to fix some of these values like: toyouta -> toyota

(Note that not all values have mistakes such as volvo, toyota etc)

I've tried making a dictionary where key is the correct word and value is the word to be corrected and then map that onto my series.

This is how my code looks:

corrections = {'maxda': 'mazda', 'porcshce': 'porsche', 'toyota': 'toyouta', 'vokswagen': 'vw', 'volkswagen': 'vw'}
df.brands = df.brands.map(corrections)

print(df.brands.unique())
>>> [nan, 'mazda', 'porsche', 'toyouta', 'vw']

As you can see the problem is that this way, all values not present in the dictionary are automatically converted to nan. One solution is to map all the correct values to themselves, but I was hoping there could be a better way to go about this.

what about `df.brands.map(corrections).fillna(df.brands)` ?? — anky, Apr 25 '19 at 08:55

jezrael · Accepted Answer · 2019-04-25T08:57:20.520

3

Use:

df.brands = df.brands.map(corrections).fillna(df.brands)

Or:

df.brands = df.brands.map(lambda x: corrections.get(x, x))

Or:

df.brands = df.brands.replace(corrections)

edited Apr 25 '19 at 08:57

answered Apr 25 '19 at 08:56

jezrael

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Is this not a dupe...? – cs95 Apr 25 '19 at 08:57
@cs95 - be free close if find it. – jezrael Apr 25 '19 at 08:57
1

There's no point, it has already been answered. Although I think [this link](https://stackoverflow.com/a/41678874/4909087) (second answer) might help. – cs95 Apr 25 '19 at 08:58
How did you quickly find the dupe questions? @cs95 – DDGG Apr 25 '19 at 09:01
While all of them work wonderfully, is there any reason to use one over the other? afaik all of them are vectorized functions? – Aakash Dusane Apr 25 '19 at 09:05
1

@AakashDusane - I think `map` with dict and fillna should be vectorized, `replace` and `map` with `get` not. there are loops under the hood – jezrael Apr 25 '19 at 09:08

How do I use mapping of dictionary for value correction?

1 Answers1