[issue35889] sqlite3.Row doesn't have useful repr

[Berker Peksag]

Berker Peksag  added the comment:

Let's close it as rejected. Thank you everyone for your input.

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resolution:  -> rejected
stage: patch review -> resolved
status: open -> closed

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[issue35889] sqlite3.Row doesn't have useful repr

[Erlend E. Aasland]

Erlend E. Aasland  added the comment:

See:
- https://www.sqlite.org/c3ref/column_database_name.html
- https://www.sqlite.org/c3ref/table_column_metadata.html

Notice that the former is only available if SQLITE_ENABLE_COLUMN_METADATA was 
defined at compile time.

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[issue35889] sqlite3.Row doesn't have useful repr

[Erlend E. Aasland]

Erlend E. Aasland  added the comment:

> What about a __repr__ that includes the primary key value(s) (for tables 
> where that is defined)?

I’d rather have that as a Row method, or read-only property. It should be 
straight-forward to implement. SQLite provides an API for such purposes.

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[issue35889] sqlite3.Row doesn't have useful repr

[Catherine Devlin]

Catherine Devlin  added the comment:

What about a __repr__ that includes the primary key value(s) (for tables where 
that is defined)?  That would be useful and informative, and also generally 
short.

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nosy: +Catherine.Devlin

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[issue35889] sqlite3.Row doesn't have useful repr

[Erlend Egeberg Aasland]

Erlend Egeberg Aasland  added the comment:

Suggesting to either close this or add an example to the docs. Up to Berker / 
Serhiy.

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Added file: https://bugs.python.org/file49942/patch.diff

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[issue35889] sqlite3.Row doesn't have useful repr

[Erlend Egeberg Aasland]

Erlend Egeberg Aasland  added the comment:

Even better, let's keep Row as it is and just add this as an example in the 
docs. If a verbose repr is needed, it's easy to override __repr__.

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[issue35889] sqlite3.Row doesn't have useful repr

[Erlend Egeberg Aasland]

Erlend Egeberg Aasland  added the comment:

AFAICS, this is fixed by the attached one-liner, based on Serhiy's suggestion 
(based on Raymond's suggestion).


$ python3.10 test.py

$ ./python.exe test.py  # patch applied

$ cat test.py
import sqlite3
cx = sqlite3.connect(":memory:")
cx.row_factory = sqlite3.Row
query = """
  select
1 as number,
'two' as string,
x'1f' as blob
"""
for row in cx.execute(query):
print(repr(row))


If Berker & Serhiy approves, I'll create a PR for it.

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nosy: +erlendaasland
Added file: https://bugs.python.org/file49941/patch.diff

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[issue35889] sqlite3.Row doesn't have useful repr

[Vlad Shcherbina]

Vlad Shcherbina  added the comment:

1. "This patch adds too many lines of code and not enough value."
If the maintainers judge it so, I have nothing to say. You have the 
responsibility to keep the codebase relatively simple.

2a. "Existing programs made with the assumption that repr(row) is short (albeit 
useless) will break when it becomes not so short."
I have no experience maintaining popular language implementations, so I defer 
to your judgement on what level of backward compatibility is warranted.

2b. "New users of new repr(row) will run into problems because its size is 
unbounded."
I think this objection is invalid, as I explained in the comment: 
https://bugs.python.org/issue35889#msg336291

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[issue35889] sqlite3.Row doesn't have useful repr

[Raymond Hettinger]

Raymond Hettinger  added the comment:

If this goes forward, the maximum output size needs to be limited in some way 
(like what is done in reprlib).

Given Serhiy's doubts, I'm only +0 on this.  Feel free to close this if you 
like.  For the most part, I don't think people even look at Row objects.

--
versions: +Python 3.9 -Python 3.8

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[issue35889] sqlite3.Row doesn't have useful repr

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

I have the same doubts as Berker. sqlite3.Row represents a data from a 
database. Databases are used in particularly for storing a large amount of data 
which can not be all loaded in RAM. Therefore sqlite3.Row can contain a data 
with a very long repr.

If you need to inspect the sqlite3.Row object, it is easy to convert it to a 
list. If you want to see keys together with values, it is not hard to make a 
list of key-value pairs or a dict: list(zip(row.keys(), row)) or 
dict(zip(row.keys(), row)).

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[issue35889] sqlite3.Row doesn't have useful repr

[Vlad Shcherbina]

Vlad Shcherbina  added the comment:

There is no need to add explicit knowledge of reprlib to the Row object or vice 
versa.

Those who use reprlib to limit output size will have no problem. Reprlib 
already truncates arbitrary reprs at the string level: 
https://github.com/python/cpython/blob/22bfe637ca7728e9f74d4dc8bb7a15ee2a913815/Lib/reprlib.py#L144

Those who use builtin repr() have to be prepared for the possibility of 
unbounded repr anyway, because all collection-like objects in Python have 
unbounded __repr__.

It would be annoying if some collection-like objects decided to be clever and 
omit parts of their regular __repr__ because they feel it's too much for the 
user to handle.

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[issue35889] sqlite3.Row doesn't have useful repr

[Berker Peksag]

Change by Berker Peksag :


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pull_requests:  -11844

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[issue35889] sqlite3.Row doesn't have useful repr

[Berker Peksag]

Change by Berker Peksag :


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pull_requests:  -11845

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[issue35889] sqlite3.Row doesn't have useful repr

[Berker Peksag]

Berker Peksag  added the comment:

While the proposed formats look nice for artificial inputs, the Row object can 
have more than two fields and the value of a field can be much longer than 
that. So, in practice the new repr can make the situation worse than the 
current repr.

I think wrapping the output of row.keys() 
(https://docs.python.org/3/library/sqlite3.html#sqlite3.Row.keys) with 
something like reprlib.recursive_repr() would work better for Row objects with 
several fields.

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nosy: +berker.peksag

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[issue35889] sqlite3.Row doesn't have useful repr

[Berker Peksag]

Change by Berker Peksag :


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pull_requests:  -11846

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[issue35889] sqlite3.Row doesn't have useful repr

[Roundup Robot]

Change by Roundup Robot :


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keywords: +patch, patch, patch, patch
pull_requests: +11844, 11845, 11846, 11847
stage:  -> patch review

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[issue35889] sqlite3.Row doesn't have useful repr

[Roundup Robot]

Change by Roundup Robot :


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pull_requests: +11844, 11845
stage:  -> patch review

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[issue35889] sqlite3.Row doesn't have useful repr

[Roundup Robot]

Change by Roundup Robot :


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pull_requests: +11844
stage:  -> patch review

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[issue35889] sqlite3.Row doesn't have useful repr

[Roundup Robot]

Change by Roundup Robot :


--
keywords: +patch, patch, patch
pull_requests: +11844, 11845, 11847
stage:  -> patch review

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[issue35889] sqlite3.Row doesn't have useful repr

[Raymond Hettinger]

Raymond Hettinger  added the comment:

+1 from me.  We're already made regular expression match objects less opaque 
and that has been useful.  There's no need for a python-ideas discussion for 
this.

If a repr doesn't round-trip, we generally put it angle brackets (see PEP 8):

>>> re.search(r'([a-z]+)(\d*)', 'alpha7')


The Row object access style uses square brackets and has a keys() method.  That 
suggests a dict-like representation would be intuitive and match how Row 
objects are used:  ro['salary'] and ro.keys().

Putting those two ideas together we get:



Note the OP's suggestion for keyword argument style doesn't make sense for two 
reasons: 1) Row objects don't allow attribute access (i.e. ro.name is invalid) 
and 2) the field names are not required to be valid Python identifiers (i.e. 
ro['class'] is possible but ro.class is syntactically invalid because "class" 
is a keyword).

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nosy: +rhettinger

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[issue35889] sqlite3.Row doesn't have useful repr

[Terry J. Reedy]

Terry J. Reedy  added the comment:

Enhancements only go into future versions.

This would have the same pluses and minuses as printing dicts in full.  I don't 
know the general feeling about expanding the classes printed out like this, or 
whether Gerhard is still active.  If you don't get responses within a few days, 
you might try posting to python-ideas list.

--
nosy: +ghaering, terry.reedy
versions:  -Python 2.7, Python 3.4, Python 3.5, Python 3.6, Python 3.7

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[issue35889] sqlite3.Row doesn't have useful repr

[Vlad Shcherbina]

New submission from Vlad Shcherbina :

To reproduce, run the following program:

import sqlite3
conn = sqlite3.connect(':memory:')
conn.row_factory = sqlite3.Row
print(conn.execute("SELECT 'John' AS name, 42 AS salary").fetchone())

It prints ''.
It would be nice if it printed something like "sqlite3.Row(name='Smith', 
saraly=42)" instead.
It wouldn't satisfy the 'eval(repr(x)) == x' property, but it's still better 
than nothing.

If the maintainers agree this is useful, I'll implement.

--
components: Library (Lib)
messages: 334746
nosy: vlad
priority: normal
severity: normal
status: open
title: sqlite3.Row doesn't have useful repr
type: enhancement
versions: Python 2.7, Python 3.4, Python 3.5, Python 3.6, Python 3.7, Python 3.8

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