First some info on wide and long formats on Wikipedia. The subject of this post is how to switch from one format to the other.

Why is that necessary?

Well, for me it’s software requirements. For example, some Javascript libraries require that the data be in the long format. So here is how to do that. First let’s GET the table from Wikipedia

import pandas as pd
url='https://en.wikipedia.org/wiki/Wide_and_narrow_data'
t=pd.read_html(url)
t0=t[0]
t0_headers=t0.loc[0]
wide = t0.drop(0)
wide.columns=t0_headers

Wide to Long

Here is the table in wide format

Person Age Weight Height
1 Bob 32 128 180
2 Alice 24 86 175
3 Steve 64 95 165 
long = pd.melt(wide,
        id_vars='Person',
        var_name='Variable', 
        value_name='Value')

Here is the same table in long format

Person Variable Value
0 Bob Age 32
1 Alice Age 24
2 Steve Age 64
3 Bob Weight 128
4 Alice Weight 86
5 Steve Weight 95
6 Bob Height 180
7 Alice Height 175
8 Steve Height 165

Want a JSON?

print(long.to_json(orient='records'))

The resule is below

[{"Person":"Bob","Variable":"Age","Value":"32"},{"Person":"Alice","Variable":"Age","Value":"24"},{"Person":"Steve","Variable":"Age","Value":"64"},{"Person":"Bob","Variable":"Weight","Value":"128"},{"Person":"Alice","Variable":"Weight","Value":"86"},{"Person":"Steve","Variable":"Weight","Value":"95"},{"Person":"Bob","Variable":"Height","Value":"180"},{"Person":"Alice","Variable":"Height","Value":"175"},{"Person":"Steve","Variable":"Height","Value":"165"}]

Long to Wide

Later. 😀