Method chaining with pipe in Python

pipe puts your own function in a chain, so the whole transform reads top to bottom.

import pandas as pd


def add_wpm(frame, chars_per_word=5):
    return frame.assign(
        wpm=(frame["chars"] / chars_per_word / (frame["seconds"] / 60)))


def only_fast(frame, floor=70):
    return frame[frame["wpm"] >= floor]


runs = pd.DataFrame({"chars": [420, 200, 610], "seconds": [60.0, 60.0, 60.0]})

result = (runs
          .pipe(add_wpm)
          .pipe(only_fast, floor=50)
          .sort_values("wpm", ascending=False)
          .round(1))
print(result)

How it works

1. Each step takes a frame and returns a frame.
2. No intermediate variables means no stale ones.
3. pipe passes extra arguments through to your function.

Keywords and builtins used here

• add_wpm
• as
• def
• only_fast
• print
• return

The run, in numbers

Lines

20

Characters to type

416

Tokens

137

Three-star pace

105 tpm

At the three-star pace of 105 tokens a minute, this run takes about 78 seconds.

Type this snippet

Step 3 of 5 in Deriving columns, step 11 of 26 in pandas.

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