Pandas data frame column : Error while replacing string value with number

Question

I have pandas dataframe column which has integers and 'NA' values. Followinareis the unique values of the column

 print(testData.LotFrontage.unique())  

 ['80' '81' '74' '78' '43' '75' 'NA' '63' '85' '70' '26' '21' '24']

I need to replace this string NA with integer 0. I tried following code

NAReplace = {'NA': 0}

trainingData.LotFrontage = [NAReplace[item] for item in trainingData.LotFrontage ]

and I am getting an error

    trainingData.LotFrontage = [NAReplace[item] for item in trainingData.LotFrontage ]
KeyError: '65'

What is the reason for this issue? Is there any other way to do this?

U13-Forward · Accepted Answer · 2018-12-24 23:55:09Z

1

Because, in the list comprehension, your getting the value i the dictionary for all value,

80 81 ..

The dictionary will be trying to find those keys that are also not 'NA', so you have to do get:

trainingData.LotFrontage = [NAReplace.get(item,item) for item in trainingData.LotFrontage ]

Also, pandasicer will be:

testData['LotFrontage'] = pd.to_numeric(testData['LotFrontage'],errors='coerce').fillna(0)

And another one from jpp's answer.

But to add something to jpp's first one:

testData['LotFrontage'].replace('NA', 0,inplace=True)

answered Dec 24, 2018 at 23:55

U13-Forward

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jpp · Accepted Answer · 2018-12-24 23:54:55Z

1

The reason is NAReplace is defined as a dictionary, and the syntax NAReplace[item] requires item is a key of NAReplace, otherwise you see a KeyError.

A list comprehension isn't appropriate here in any case. Just use fillna:

testData['LotFrontage'] = testData['LotFrontage'].replace('NA', 0)

Most likely you want numeric data, in which case I suggest you convert to numeric:

testData['LotFrontage'] = pd.to_numeric(testData['LotFrontage'], errors='coerce').fillna(0)

The argument errors='coerce' forces non-convertible values to give NaN.

answered Dec 24, 2018 at 23:54

jpp

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1 Comment

U13-Forward Over a year ago

Well, both at the same time on pd.to_numeric one.

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