slicing
Slicing is a way of accessing a part of a sequence by specifying a start, stop, and step. As with normal indexing, negative numbers can be used to count backwards.
Examples
>>> letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
>>> letters[2:] # from element 2 to the end
['c', 'd', 'e', 'f', 'g']
>>> letters[:4] # up to element 4
['a', 'b', 'c', 'd']
>>> letters[3:5] # elements 3 and 4 -- the right bound is not included
['d', 'e']
>>> letters[2:-1:2] # Every other element between 2 and the last
['c', 'e']
>>> letters[::-1] # The whole list in reverse
['g', 'f', 'e', 'd', 'c', 'b', 'a']
>>> words = "Hello world!"
>>> words[2:7] # Strings are also sequences
"llo w"
ytdl
Per Python Discord's Rule 5, we are unable to assist with questions related to youtube-dl, pytube, or other YouTube video downloaders, as their usage violates YouTube's Terms of Service.
For reference, this usage is covered by the following clauses in YouTube's TOS, as of 2021-03-17:
The following restrictions apply to your use of the Service. You are not allowed to:
1. access, reproduce, download, distribute, transmit, broadcast, display, sell, license, alter, modify or otherwise use any part of the Service or any Content except: (a) as specifically permitted by the Service; (b) with prior written permission from YouTube and, if applicable, the respective rights holders; or (c) as permitted by applicable law;
3. access the Service using any automated means (such as robots, botnets or scrapers) except: (a) in the case of public search engines, in accordance with YouTube’s robots.txt file; (b) with YouTube’s prior written permission; or (c) as permitted by applicable law;
9. use the Service to view or listen to Content other than for personal, non-commercial use (for example, you may not publicly screen videos or stream music from the Service)