Why is the python formatting giving me this error:
>>> type(df['rMeanPSFMag'])
pandas.core.series.Series
Convert the format of the rMeanPSFMag column::
>>> df['rMeanPSFMag'] = df['rMeanPSFMag'].map('{:,.3f}'.format)
>>> type(df['rMeanPSFMag'])
pandas.core.series.Series
>>> df['rMeanPSFMag'] = df['rMeanPSFMag'].map('{:,.3f}'.format)
I then get a ValueError: Unknown format code 'f' for object of type 'str'
It is expected, because column have string values, so if convert again from float it raise error:
df = pd.DataFrame({'rMeanPSFMag':[10.10235, 45.45871]})
print(df['rMeanPSFMag'].apply(type))
0 <class 'float'>
1 <class 'float'>
Name: rMeanPSFMag, dtype: object
#convert floats to strings with 3 decimals
df['rMeanPSFMag'] = df['rMeanPSFMag'].map('{:,.3f}'.format)
print(df)
rMeanPSFMag
0 10.102
1 45.459
print(df['rMeanPSFMag'].apply(type))
0 <class 'str'>
1 <class 'str'>
Name: rMeanPSFMag, dtype: object
If want float to 3 decimals use round:
df['rMeanPSFMag'] = df['rMeanPSFMag'].round(3)
print (df)
rMeanPSFMag
0 10.102
1 45.459
print(df['rMeanPSFMag'].apply(type))
0 <class 'float'>
1 <class 'float'>
Name: rMeanPSFMag, dtype: object
Another solution is multiple by 1000, convert to integers and divide by 1000:
df['rMeanPSFMag'] = df['rMeanPSFMag'].mul(1000).astype(int).div(1000)
print (df)
rMeanPSFMag
0 10.102
1 45.458
df['rMeanPSFMag'] = df['rMeanPSFMag'].round(3)?