使用变量中的方法在pandas中重新采样

Question

Pandas changed its resample API on version 18.1. The reduction methods are no longer a argument to the resample method, but they are their own methods.

Example:

import pandas as pd
import numpy as np

rng = pd.date_range('1/1/2012', periods=100, freq='S')
ts = pd.Series(np.random.randint(0, 500, len(rng)), index=rng)

#Old API
ts.resample('5Min', how='sum')

#New API
ts.resample('5Min').sum()

I had some code that acted like this:

def my_func(my_series, how="sum"):
    #Do some stuff before
    my_series.resample('5Min' how=how)

How do I make this with the new API? I want my_func to be able to call the resample method with different reduction methods.

One answer already covers the case when the "how" is a just an aggregation function. I had more in mind cases where we want to perform upsampling.

Eg:

#Old API:
ts.resample('250L', fill_method='ffill')
#New API
ts.resample('250L').ffill()

Note that on my real code I have something more close to this:

def my_func(dummy_df, freq="10Min", how="last", label="right", closed="right", fill_method="ffill"):
    dummy_df.resample(freq, how=how, label=label, closed=closed, fill_method=fill_method)

and want to write it again with the new API.

Confusingly the documentation still (26.07.2016) has this line:

Any function available via dispatching can be given to the how parameter by name, including sum, mean, std, sem, max, min, median, first, last, ohlc.

But the how parameter is supposed to become deprecated.

Answer 1

Solution with Resampler.agg :

print (ts.resample('5Min').agg('sum'))

---

print (ts.resample('5Min').sum())
2012-01-01    24223
Freq: 5T, dtype: int32

print (ts.resample('5Min').agg('sum'))
2012-01-01    24223
Freq: 5T, dtype: int32

So custom function is:

def my_func(my_series, how="sum"):
    #Do some stuff before
    return my_series.resample('5Min').agg(how)

print (my_func(ts))
2012-01-01    24223
Freq: 5T, dtype: int32

Answer 2

segregate how and fill_method and pass them through getattr :

def my_func(dummy_df, freq="10Min", how="last",
            label="right", closed="right", fill_method="ffill"):
    resample = dummy_df.resample(freq, label=label, closed=closed)
    return getattr(getattr(resample, how)(), fill_method)()