Script that uses youtube-dl to calculate total size of all videos in a playlist (also works with single videos). Now at this repo: https://github.com/theychx/totalsize

ytdl_totalsize.py

#! /usr/bin/env python3

import math
import sys

import youtube_dl


BEST_FORMAT = "bestvideo+bestaudio/best"


class ResourceNotFoundError(Exception):
    pass


class NoFilesizeError(Exception):
    pass


class TotalSize:
    def __init__(self, url):
        self._ydl = youtube_dl.YoutubeDL({"quiet": True, "no_warnings": True})
        self._selector = self._ydl.build_format_selector(BEST_FORMAT)
        try:
            preinfo = self._ydl.extract_info(url, process=False)
        except youtube_dl.utils.DownloadError:
            raise ResourceNotFoundError
        if 'entries' in preinfo:
            self._videos = list(preinfo['entries'])
        else:
            self._videos = [preinfo]
        self.number_of_videos = len(self._videos)
        
    def _get_size(self, info):
        try:
            video = self._ydl.process_ie_result(info, download=False)
        except youtube_dl.utils.DownloadError:
            raise NoFilesizeError
        try:
            best = next(self._selector(video))
        except KeyError:
            best = video
        try:
            if 'requested_formats' in best:
                size = sum(int(f['filesize']) for f in best['requested_formats'])
            else:
                size = int(best['filesize'])
        except (TypeError, KeyError):
            raise NoFilesizeError
        return size
    
    def _readable_size(self, size_bytes):
        if size_bytes == 0:
            return "0B"
        size_name = ("B", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB")
        i = int(math.floor(math.log(size_bytes, 1024)))
        p = math.pow(1024, i)
        s = round(size_bytes / p, 2)
        return "%s %s" % (s, size_name[i])

    def get_totalsize(self):
        totalsize = 0
        for video in self._videos:
            try:
                size = self._get_size(video)
            except NoFilesizeError:
                print('Filesize of "%s" is unavailable.' % video['title'], file=sys.stderr)
            else:
                print('"%s": %s' % (video['title'], self._readable_size(size)))
                totalsize += size
        return self._readable_size(totalsize)


def main(url):
    total = TotalSize(url)
    print('Total size of all videos with reported filesize: ' + total.get_totalsize())
    print('Total number of videos: %s' % total.number_of_videos)


if __name__ == '__main__':
    try:
        main(sys.argv[1])
    except IndexError:
        sys.exit('Please supply an url.')
    except ResourceNotFoundError:
        sys.exit('Resource not found.')

Hey! I just found about this tool, and love it, but it doesn't work for whole youtube channels, only for playlists. Could you maybe update it to work with whole channels?

@bathrobehero I've improved the script a bit (including the functionality you requested) and uploaded it to pypi. Feel free to open tickets for bug reports or further feature requests here.