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pandas python

applying a function to all the entries from a ; delimited column (map? pandas?)

发布于 2020-03-27 15:38:46

I have the following data frame and would like to replace the values (delimiter = ";") of the third column.

cat file.text

Name         ID        Values
John         81-502    1
Mike         81-501    2;2;2
Matthew      81-512    1,0

def fun(x):
     return x+1

I would like to apply this function to replace the Values column in my dataframe such that:

cat out.txt

Name         ID        Values
John         81-502    2
Mike         81-501    3;3;3
Matthew      81-512    2;1
Questioner
user171558
Viewed
18
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jezrael 2020-01-31 16:24

First is necessary split values, convert to integers, add 1, convert to strings and join back by ;:

df['Values'] = df['Values'].apply(lambda x: ';'.join(str(int(y) + 1) for y in x.split(';')))

Solution with list comprehension:

df['Values'] = [ ';'.join(str(int(y) + 1) for y in x.split(';')) for x in df['Values']]

print (df)
      Name      ID Values
0     John  81-502      2
1     Mike  81-501  3;3;3
2  Matthew  81-512    2;1
user171558 2020-02-02 14:15:02

Quick issue! What if df['Values'][0]==NaN

jezrael 2020-02-02 14:16:09

@user171558 - then use .apply(lambda x: ';'.join(str(int(y) + 1) for y in x.split(';')) if pd.notna(x) else np.nan)

user171558 2020-02-02 14:44:48

In my actual df, I have strings that I feed into a package function. and my values column consists of strings. Would it be ok if I used pd.NA instead of np.nan? After some reading, I assume they're very similar

jezrael 2020-02-02 14:45:59

@user171558 - I think it is same :)

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