io.BytesIO does not have peek()

[marcelm]

BPO	46375
Nosy	@benjaminp, @marcelm, @kumaraditya303
PRs	gh-90533: Implement BytesIO.peek() #30808

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2022-01-14.10:39:24.835>
labels = ['type-feature', 'library', '3.11']
title = 'io.BytesIO does not have peek()'
updated_at = <Date 2022-01-22.22:08:29.533>
user = 'https://github.com/marcelm'

bugs.python.org fields:

activity = <Date 2022-01-22.22:08:29.533>
actor = 'marcelm'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2022-01-14.10:39:24.835>
creator = 'marcelm'
dependencies = []
files = []
hgrepos = []
issue_num = 46375
keywords = ['patch']
message_count = 2.0
messages = ['410552', '411294']
nosy_count = 4.0
nosy_names = ['benjamin.peterson', 'stutzbach', 'marcelm', 'kumaraditya']
pr_nums = ['30808']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue46375'
versions = ['Python 3.11']

[marcelm]

It would be great to be able to use peek() on BytesIO objects.

I have a function that gets passed a file-like object and uses peek() on it. This works for nearly all types of files relevant in my library, except BytesIO instances (which I use during testing), for which I need to add a small workaround using tell() and seek().

[marcelm]

I opened a PR, but I now wonder whether the missing peek() is by design.

First, I noticed that instead of using BytesIO directly, I can wrap the instance in an io.BufferedReader, which does have peek(). (It’s just a bit inconvenient.)

The second thing is that BytesIO is currently documented to inherit from BufferedIOBase, but if peek() is implemented, one could argue that BytesIO now should inherit from BufferedReader because it then has all the methods. And that seems to great a change from my perspective.

I’ll defer to someone more knowledgeable and do not mind at all if this issue is closed without action.