Convert 2-column counter-like csv file to Python collections.Counter?

问题

I have a comma separated (,) tab delimited (\t), file.

68,"phrase"\t
485,"another phrase"\t
43, "phrase 3"\t

Is there a simple approach to throw it into a Python Counter?

回答1:

You could use a dictionary comprehension, is considered more pythonic and it can be marginally faster:

import csv
from collections import Counter


def convert_counter_like_csv_to_counter(file_to_convert):
    with file_to_convert.open(encoding="utf-8") as f:
        csv_reader = csv.DictReader(f, delimiter="\t", fieldnames=["count", "title"])
        the_counter = Counter({row["title"]: int(float(row["count"])) for row in csv_reader})
    return the_counter

回答2:

I couldn't let this go and stumbled on what I think is the winner.

In testing it was clear that looping through the rows of the csv.DictReader was the slowest part; taking about 30 of the 40 seconds.

I switched it to simple csv.reader to see what I would get. This resulted in rows of lists. I wrapped this in a dict to see if it directly converted. It did!

Then I could loop through a native dictionary instead of a csv.DictReader.

The result... done with 4 million rows in 3 seconds! 🎉

def convert_counter_like_csv_to_counter(file_to_convert):
    with file_to_convert.open(encoding="utf-8") as f:
        csv_reader = csv.reader(f, delimiter="\t")
        d = dict(csv_reader)
        the_counter = Counter({phrase: int(float(count)) for count, phrase in d.items()})

    return the_counter

回答3:

Here's my best attempt. It works but isn't the fastest.
~~Takes about 1.5 minutes to run on a 4 million line input file.~~
Now takes about 40 seconds on a 4 million line input file after the suggestion by Daniel Mesejo.

_{Note: the count value in the csv can be in scientific notation and needs conversion. Hence the int(float( casting.}

import csv
from collections import Counter

def convert_counter_like_csv_to_counter(file_to_convert):

    the_counter = Counter()
    with file_to_convert.open(encoding="utf-8") as f:
        csv_reader = csv.DictReader(f, delimiter="\t", fieldnames=["count", "title"])
        for row in csv_reader:
            the_counter[row["title"]] = int(float(row["count"]))

    return the_counter

来源：https://stackoverflow.com/questions/53642743/convert-2-column-counter-like-csv-file-to-python-collections-counter

标签

python

python-3.x

python-collections