Find the range of all columns (difference between maximum and minimum) while gracefully handling string columns

Question

I have a scenario where I have to find the range of all the columns in a dataset which contains multiple columns with numeric value but one column has string values. Please find sample records from my data set below:

import seaborn as sns
iris = sns.load_dataset('iris')

   sepal_length  sepal_width  petal_length  petal_width species
0           5.1          3.5           1.4          0.2  setosa
1           4.9          3.0           1.4          0.2  setosa
2           4.7          3.2           1.3          0.2  setosa
3           4.6          3.1           1.5          0.2  setosa
4           5.0          3.6           1.4          0.2  setosa

The maximum and minimum of these columns are given by

sepal_length          7.9
sepal_width           4.4
petal_length          6.9
petal_width           2.5
species         virginica
dtype: object

and

sepal_length       4.3
sepal_width          2
petal_length         1
petal_width        0.1
species         setosa
dtype: object

...respectively. To find the range of all the columns I can use the below code:

iris.max() - iris.min()

But as the column 'species' has string values, the above code is throwing the below error:

TypeError: unsupported operand type(s) for -: 'str' and 'str'

If the above error occurs, I want to print the value as the

"{max string value}" - "{min string value}"

IOW, my expected output would be something like:

sepal_length                   3.6
sepal_width                    2.4
petal_length                   5.9
petal_width                    2.4
species         virginica - setosa

How do I resolve this issue?

Answer 1

Handle the numeric and string columns separately. You can select these using df.select_dtypes . Finally, concat the result.

u = Iris.select_dtypes(include=[np.number])
# U = u.apply(np.ptp, axis=0)
U = u.max() - u.min()

v = Iris.select_dtypes(include=[object])
V = v.max() + ' - ' + v.min()

U.append(V)

sepal_length                   3.6
sepal_width                    2.4
petal_length                   5.9
petal_width                    2.4
species         virginica - setosa
dtype: object