Why is python pandas dataframe rounding my values?

I could reproduce this behaviour by setting the pd.options.display.precision to 0:

In [4]: df['genes/SCM'] = df['genes']/df['SCM']

In [5]: df
Out[5]:
   genome  contig  genes  SCM  genes/SCM
0   20900      48      1    0        inf
1   20900      37    130  103   1.262136
2   20900      35      1    1   1.000000
3   20900       1     79   66   1.196970
4   20900      66      5    3   1.666667

In [6]: pd.options.display.precision = 0

In [7]: df
Out[7]:
   genome  contig  genes  SCM  genes/SCM
0   20900      48      1    0        inf
1   20900      37    130  103          1
2   20900      35      1    1          1
3   20900       1     79   66          1
4   20900      66      5    3          2

Check your Pandas & Numpy options