dtoolkit.transformer.EvalTF

class dtoolkit.transformer.EvalTF(*args, **kwargs)

A transformer could evaluate a string describing operations on DataFrame columns.

See also

pandas.DataFrame.eval

This transformer’s prototype method.

Notes

eval()’s inplace parameter is not work for this transformer. Actually this break pipeline stream. If a transformer’s inplace is True, the next tf input would get None.

Examples

>>> import pandas as pd
>>> from dtoolkit.transformer import EvalTF
>>> df = pd.DataFrame({'A': range(1, 6), 'B': range(10, 0, -2)})
>>> df
    A   B
0  1  10
1  2   8
2  3   6
3  4   4
4  5   2
>>> tf = EvalTF('A + B')
>>> tf.transform(df)
0    11
1    10
2     9
3     8
4     7
dtype: int64

Assignment is allowed though by default the original DataFrame is not modified.

>>> tf = EvalTF('C = A + B')
>>> tf.transform(df)
    A   B   C
0  1  10  11
1  2   8  10
2  3   6   9
3  4   4   8
4  5   2   7
>>> df
    A   B
0  1  10
1  2   8
2  3   6
3  4   4
4  5   2

Multiple columns can be assigned to using multi-line expressions:

>>> tf = EvalTF(
...     '''
... C = A + B
... D = A - B
... '''
... )
>>> tf.transform(df)
    A   B   C  D
0  1  10  11 -9
1  2   8  10 -6
2  3   6   9 -3
3  4   4   8  0
4  5   2   7  3

Attributes:

inverse_transform_method

Methods

fit(*_)	Fit transformer.
fit_transform(X[, y])	Fit to data, then transform it.
inverse_transform(X)	Undo transform to X.
set_output(*[, transform])	Set output container.
transform(X)	Transform X.
transform_method(self, expr, *[, inplace])	Evaluate a string describing operations on DataFrame columns.
update_invargs(*args, **kwargs)	Inverse transform method argument entry.