Formatting numeric columns of a pandas data frame with a specified number of decimal digits

Question

I have to format a column of numbers in a data frame pandas rounding for two but with three decimal digits where the last is 0 and the column does not have to be a string. The numbers of this column must be represented so once exported to Excel.

d = {'col1': [0.567, 2.54765476], 'col2': [3, 4]}
df = pd.DataFrame(data=d)

         col1  col2
0       0.567     3
1  2.54765476     4

expected:

    col1  col2
0  0.560     3
1  2.540     4

It is important that the type remain numerical

Possible duplicate of [Customized float formatting in a pandas DataFrame](https://stackoverflow.com/questions/42735541/customized-float-formatting-in-a-pandas-dataframe) — G. Anderson, Feb 19 '19 at 16:40
Is it important to you that it be `2.540` and not `2.550` - ie truncating the float as opposed to rounding? — Josh Friedlander, Feb 19 '19 at 16:46

score 1 · Answer 1 · answered Feb 19 '19 at 16:46

1

You may need floor div then format

df.col1=(np.floor(df.col1*100)/100).map('{:,.3f}'.format)
df
Out[355]: 
    col1  col2
0  0.560     3
1  2.540     4

answered Feb 19 '19 at 16:46

BENY

317,841
20
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I had tried this solution but it is not good because map transforms the number into string. – stefanodv Feb 19 '19 at 16:51

score 0 · Answer 2 · answered Feb 20 '19 at 07:33

If, as you say, you need rounding rather than string truncation, then assuming your second value should be 2.550, you can use Pandas float display options, as linked to here by @G. Anderson:

pd.options.display.float_format = '{:,.3f}'.format
df.col1 = df.col1.round(2)
df
>   
    col1    col2
0   0.570   3
1   2.550   4

Formatting numeric columns of a pandas data frame with a specified number of decimal digits

2 Answers2