How to replace column values based on a list?

Question

I have a list like this:

x = ['Las Vegas', 'San Francisco, 'Dallas']

And a dataframe that looks a bit like this:

import pandas as pd
data = [['Las Vegas (Clark County), 25], ['New York', 23], 
        ['Dallas', 27]]
df = pd.DataFrame(data, columns = ['City', 'Value'])

I want to replace my city values in the DF "Las Vegas (Clark County)" with "Las Vegas". In my dataframe are multiple cities with different names which needs to be changed. I know I could do a regex expression to just strip off the part after the parentheses, but I was wondering if there was a more clever, generic way.

jezrael · Accepted Answer · 2019-12-01 07:58:16Z

2

Use Series.str.extract with joined values of list by | for regex OR and then replace non matched values to original by Series.fillna:

df['City'] = df['City'].str.extract(f'({"|".join(x)})', expand=False).fillna(df['City'])
print (df)
        City  Value
0  Las Vegas     25
1   New York     23
2     Dallas     27

Another idea is use Series.str.contains with loop, but it should be slow if large Dataframe and many values in list:

for val in x:
    df.loc[df['City'].str.contains(val), 'City'] = val

answered Dec 1, 2019 at 7:58

jezrael

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