python - Pandas: unable to change column data type -
i following advice here change column data type of pandas dataframe. however, not seem work if reference columns index numbers instead of column names. there way correctly?
in [49]: df.iloc[:, 4:].astype(int) out[49]: <class 'pandas.core.frame.dataframe'> int64index: 5074 entries, 0 5073 data columns (total 3 columns): 5 5074 non-null values 6 5074 non-null values 7 5074 non-null values dtypes: int64(3) in [50]: df.iloc[:, 4:] = df.iloc[:, 4:].astype(int) in [51]: df out[51]: <class 'pandas.core.frame.dataframe'> int64index: 5074 entries, 0 5073 data columns (total 7 columns): 1 5074 non-null values 2 5074 non-null values 3 5074 non-null values 4 5074 non-null values 5 5074 non-null values 6 5074 non-null values 7 5074 non-null values dtypes: object(7) in [52]:
do this
in [49]: df = dataframe([['1','2','3','.4',5,6.,'foo']],columns=list('abcdefg')) in [50]: df out[50]: b c d e f g 0 1 2 3 .4 5 6 foo in [51]: df.dtypes out[51]: object b object c object d object e int64 f float64 g object dtype: object need assign columns one-by-one
in [52]: k, v in df.iloc[:,0:4].convert_objects(convert_numeric=true).iteritems(): df[k] = v ....: in [53]: df.dtypes out[53]: int64 b int64 c int64 d float64 e int64 f float64 g object dtype: object convert objects right thing, easiest this
in [54]: df = dataframe([['1','2','3','.4',5,6.,'foo']],columns=list('abcdefg')) in [55]: df.convert_objects(convert_numeric=true).dtypes out[55]: int64 b int64 c int64 d float64 e int64 f float64 g object dtype: object assigning via df.iloc[:,4:] series on right-hand side copies data changing type needed, think should work in theory, suspect hitting obscure bug prevents object dtype changing real (meaning int/float) dtype. should raise now.
heres issue track this: https://github.com/pydata/pandas/issues/4312
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