Progress in bytes when reading CSV from URL with pandas

Question

Because some of the CSV files that I need to read are very large (multiple GB), I am trying to implement a progress bar that indicates the number of bytes read out of the total when reading a CSV file from a URL with pandas.

I am trying to implement something like this:

from tqdm import tqdm
import requests
from sodapy import Socrata
import contextlib
import urllib
import pandas as pd

url = "https://public.tableau.com/views/PPBOpenDataDownloads/UseOfForce-All.csv?:showVizHome=no"

response = requests.get(url, params=None, stream=True)
response.raise_for_status()
total_size = int(response.headers.get('Content-Length', 0))

block_size = 1000
df = []
last_position = 0
cur_position = 1
with tqdm(desc=url, total=total_size,
     unit='iB',
     unit_scale=True,
     unit_divisor=1024
     ) as bar:
    with contextlib.closing(urllib.request.urlopen(url=url)) as rd:
        # Create TextFileReader
        reader = pd.read_csv(rd, chunksize=block_size)
        for chunk in reader:
            df.append(chunk)
            # Here I would like to calculate the current file position: cur_position 
            bar.update(cur_position - last_position)
            last_position = cur_position

Is there a way to get the file position from the pandas TextFileReader somehow? Perhaps something equivalent to ftell in C++ for TextFileReader?

Answer 1

Not thoroughly tested, but you can implement custom class with read() method where you read from requests response line by line and update the tqdm bar:

import requests
import pandas as pd
from tqdm import tqdm

url = "https://public.tableau.com/views/PPBOpenDataDownloads/UseOfForce-All.csv?:showVizHome=no"


class TqdmReader:
    def __init__(self, resp):
        total_size = int(resp.headers.get("Content-Length", 0))

        self.resp = resp
        self.bar = tqdm(
            desc=resp.url,
            total=total_size,
            unit="iB",
            unit_scale=True,
            unit_divisor=1024,
        )

        self.reader = self.read_from_stream()

    def read_from_stream(self):
        for line in self.resp.iter_lines():
            line += b"\n"
            self.bar.update(len(line))
            yield line

    def read(self, n=0):
        try:
            return next(self.reader)
        except StopIteration:
            return ""


with requests.get(url, params=None, stream=True) as resp:
    df = pd.read_csv(TqdmReader(resp))

print(len(df))

Prints:

https://public.tableau.com/views/PPBOpenDataDownloads/UseOfForce-All.csv?:showVizHome=no: 100%|██████████████████████████████████████████████████████████████████████████████| 2.09M/2.09M [00:00<00:00, 2.64MiB/s]
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