Pandas set_Value with DatetimeIndex [Python]

Question

I'm trying to add the row-wise result from a function into my dataframe using df.set_Value.

df in the format :

    Count   DTW
DateTime        
2015-01-16  10  0
2015-01-17  28  0

Using df.setValue

dw.set_Value(idx, 'col', dtw) # idx and dtw are int values

TypeError: cannot insert DatetimeIndex with incompatible label

How do I solve this error or what alternative method with comparable efficiency is there?

jezrael · Accepted Answer · 2016-08-19 14:15:13Z

5

I think you have Series, not DataFrame, so use Series.set_value with index converted to datetime

dw = pd.Series([-2374], index = [pd.to_datetime('2015-01-18')])
dw.index.name = 'DateTime'
print (dw)
DateTime
2015-01-18   -2374
dtype: int64

print (dw.set_value(pd.to_datetime('2015-01-19'), 1))
DateTime
2015-01-18   -2374
2015-01-19       1
dtype: int64

print (dw.set_value(pd.datetime(2015, 1, 19), 1))
DateTime
2015-01-18   -2374
2015-01-19       1
dtype: int64

More standard way is use ix or iloc:

print (dw)
            Count  DTW
DateTime              
2015-01-16     10    0
2015-01-17     28    0

dw.ix[1, 'DTW'] = 10
#dw.DTW.iloc[1] = 10
print (dw)
            Count  DTW
DateTime              
2015-01-16     10    0
2015-01-17     28   10

edited Aug 19, 2016 at 14:15

answered Aug 19, 2016 at 13:51

jezrael

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5 Comments

SerialDev Over a year ago

I'm getting the idx value from a range so I wanted to allocate it directly using an int value, I think this created a problem with the index as it is not in numerical order but is instead a DateTime index. I hope this clarified my question

jezrael Over a year ago

So do you have first index with int and datetime values? Or need overwrite some value, e.g. 28 in sample? Or add new row?

SerialDev Over a year ago

I want to set a value on an existing row that has a datetime index, is there an iterable that I could use to get datetime index as opposed to int?

jezrael Over a year ago

Do you think something like dw.DTW.iloc[1] = 10 ?

SerialDev Over a year ago

For some reason that escaped me, Thank you @jezrael that worked

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