CODEWITHSUNDEEP
python-3.xpandas
Joost Döbken
Joost Döbken

Reputation: 4025

lost attribute after adding column to pandas DataFrame

I like to add attributes to pandas DataFrame columns, for example to manage labels or units.

df = pd.DataFrame([[1, 2], [5, 6]], columns=['A', 'B'])
df['A'].units = 'm/s'

Calling the units of column (with df['A'].units) returns m/s.

However, the attribute gets lost after any DataFrame to Series operation, such as adding a new column:

df['C'] = [3, 8]
df['A'].units

AttributeError: 'Series' object has no attribute 'units'

Is there an approach to keep the attributes or an alternative to add columns?

Upvotes: 0

Views: 180

Answers (1)

Zero
Zero

Reputation: 76947

_metadata, is not part of public API. Not a stable way of doing it, still, for now

In [8]: df = pd.DataFrame([[1, 2], [5, 6]], columns=['A', 'B'])

In [9]: df['A']._metadata
Out[9]: ['name']

In [10]: df['A']._metadata.append({'units': 'm/s'})

In [11]: df['C'] = [3, 8]

In [12]: df['A']._metadata
Out[12]: ['name', {'units': 'm/s'}]

Upvotes: 1

Related Questions