Document '_' in interpreter tutorial

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-07-25.12:54:28.964>
labels = ['type-bug', '3.8', '3.9', '3.10', 'docs']
title = "Document '_' in interpreter tutorial"
updated_at = <Date 2020-07-28.12:13:27.860>
user = 'https://github.com/wyz23x2'

bugs.python.org fields:

activity = <Date 2020-07-28.12:13:27.860>
actor = 'wyz23x2'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2020-07-25.12:54:28.964>
creator = 'wyz23x2'
dependencies = []
files = []
hgrepos = []
issue_num = 41394
keywords = ['patch']
message_count = 15.0
messages = ['374260', '374261', '374262', '374263', '374264', '374266', '374267', '374329', '374390', '374450', '374451', '374452', '374453', '374454', '374455']
nosy_count = 7.0
nosy_names = ['eric.smith', 'docs@python', 'remi.lapeyre', 'xtreak', 'shihai1991', 'ShubhamKJha', 'wyz23x2']
pr_nums = ['21654', '21657']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue41394'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']