CODEWITHSUNDEEP
python-3.xpandasdataframe
Hardik Gupta
Hardik Gupta

Reputation: 4790

Pandas: Every value of cell list to lower case

I have a dataframe like this

# initialize list of lists 
data = [[1, ['ABC', 'pqr']], [2, ['abc', 'XY']], [3, np.nan]] 

# Create the pandas DataFrame 
data = pd.DataFrame(data, columns = ['Name', 'Val'])
data

    Name  Val
0   1     [ABC, pqr]
1   2     [abc, XY]
2   3     NaN

I am trying to convert every value in the list, to it's lower case

data['Val'] = data['Val'].apply(lambda x: np.nan if len(x) == 0 else [item.lower() for item in x])
data

However I get this error

TypeError: object of type 'float' has no len()

Expected final output

     Name  Val
0   1     [abc, pqr]
1   2     [abc, xy]
2   3     NaN

Upvotes: 0

Views: 92

Answers (1)

jezrael
jezrael

Reputation: 862731

First idea is filter rows without missing values and processing:

m = data['Val'].notna()
data.loc[m, 'Val'] = data.loc[m, 'Val'].apply(lambda x: [item.lower() for item in x])
print (data)
   Name         Val
0     1  [abc, pqr]
1     2   [abc, xy]
2     3         NaN

Or you can processing only lists filtered by isinstance:

f = lambda x: [item.lower() for item in x] if isinstance(x, list) else np.nan
data['Val'] = data['Val'].apply(f)
print (data)
   Name         Val
0     1  [abc, pqr]
1     2   [abc, xy]
2     3         NaN

Upvotes: 1

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