plydata.helper_verbs.call

class plydata.helper_verbs.call(*args, **kwargs)

Call external function or dataframe method

This is a special verb; it turns regular functions and dataframe instance methods into verb instances that you can pipe to. It reduces the times one needs to break out of the piping workflow.

Parameters

funccallable() or str

A function that accepts a dataframe as the first argument. Dataframe methods are specified using strings and preferrably they should start with a period, e.g '.reset_index'

*argstuple

Second, third, fourth, ... arguments to func

**kwargsdict

Keyword arguments to func

Examples

>>> import pandas as pd
>>> import numpy as np
>>> from plydata import *
>>> df = pd.DataFrame({
...     'A': {0: 'a', 1: 'b', 2: 'c'},
...     'B': {0: 1, 1: 3, 2: 5},
...     'C': {0: 2, 1: 4, 2: np.nan}
... })
>>> df
   A  B    C
0  a  1  2.0
1  b  3  4.0
2  c  5  NaN

Using an external function

>>> df >> call(pd.melt)
  variable value
0        A     a
1        A     b
2        A     c
3        B     1
4        B     3
5        B     5
6        C     2
7        C     4
8        C   NaN

An external function with arguments

>>> df >> call(pd.melt, id_vars=['A'], value_vars=['B'])
   A variable  value
0  a        B      1
1  b        B      3
2  c        B      5

A method on the dataframe

>>> df >> call('.dropna', axis=1)
   A  B
0  a  1
1  b  3
2  c  5

>>> (df
...  >> call(pd.melt)
...  >> query('variable != "B"')
...  >> call('.reset_index', drop=True)
...  )
  variable value
0        A     a
1        A     b
2        A     c
3        C     2
4        C     4
5        C   NaN