[issue32300] print(os.environ.keys()) should only print the keys

[Irit Katriel]

Change by Irit Katriel :


--
type:  -> behavior
versions: +Python 3.10, Python 3.9 -Python 3.7

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[issue32300] print(os.environ.keys()) should only print the keys

[Cheryl Sabella]

Cheryl Sabella  added the comment:

Never mind.  I see it's in bytes.  I missed that the first time.  But, if it 
wasn't in bytes, would that be an OK solution?  Or is it bad to override those 
methods in that class?

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[issue32300] print(os.environ.keys()) should only print the keys

[Cheryl Sabella]

Cheryl Sabella  added the comment:

I'm missing something here, so please forgive me for asking, but why is it bad 
to add:

def keys(self):
return self._data.keys()

def values(self):
return self._data.values()

def items(self):
return self._data.items()

to the _Environ class?

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[issue32300] print(os.environ.keys()) should only print the keys

[Aaron Meurer]

Aaron Meurer  added the comment:

Can't third party code write their own proxies? Why do we have to do that?

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[issue32300] print(os.environ.keys()) should only print the keys

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

With option 4 we need to add a custom wrapper not only for Shelf's KeysView, 
but for KeysView of all similar proxy classes, including classes in third-party 
code not available for us. This is impossible.

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[issue32300] print(os.environ.keys()) should only print the keys

[Aaron Meurer]

Aaron Meurer  added the comment:

Serhiy, isn't option 4?

4. Make KeysView.__repr__ show list(self). Add a custom wrapper for Shelf's 
KeysView so that it doesn't do this. 

This seems to be what Victor is suggesting. It makes the most sense to me for 
the common (i.e., default) case to be to show the keys (and just the keys), and 
for use cases that want otherwise to subclass and modify.

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[issue32300] print(os.environ.keys()) should only print the keys

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

Options:

1. Use the subclass of KeyView with overridden __repr__ for os.environ.keys(). 
This will add a code for pretty rare use case.

2. Remove os.environ.__repr__. You can use repr(os.environ.copy()) or 
repr(dict(os.environ)) if you want to see a content.

3. Do not change anything. You can use repr(list(os.environ.keys())) if you 
want to see only keys.

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[issue32300] print(os.environ.keys()) should only print the keys

[STINNER Victor]

STINNER Victor  added the comment:

Cheryl: "Thanks!  Yes, I can work this.  It may take a few days for me to get 
to it."

It seems like we have a disagreement on how to fix this issue. We should first 
agree on the best solution.

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[issue32300] print(os.environ.keys()) should only print the keys

[STINNER Victor]

STINNER Victor  added the comment:

Currently, repr(Shelf.keys()) doesn't dump the content of the shelf:

>>> import pickle, shelve
>>> s=shelve.Shelf({b'key': pickle.dumps('value')})
>>> k=s.keys()
>>> k
KeysView()
>>> list(k)
['key']
>>> list(s.values())
['value']

I understand that changing KeysView.__repr__() changes repr(Shelf.keys()) 
behaviour.

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[issue32300] print(os.environ.keys()) should only print the keys

[Cheryl Sabella]

Cheryl Sabella  added the comment:

Victor,

Thanks!  Yes, I can work this.  It may take a few days for me to get to it.

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[issue32300] print(os.environ.keys()) should only print the keys

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

shelve.Shelf is the example of such kind.

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[issue32300] print(os.environ.keys()) should only print the keys

[STINNER Victor]

STINNER Victor  added the comment:

> Don't make KeysView.__repr__ and ValuesView.__repr__ containing the lists of 
> all keys and values. This will make the repr of the view of a mapping which 
> is a proxy of an external DB containing the full content of that DB, which 
> can be gigabytes. See for example rejected issue21670.

The current implementation displays repr(self._mapping):

class MappingView(Sized):
...
def __repr__(self):
return '{0.__class__.__name__}({0._mapping!r})'.format(self)

For your proxy example: what is the proxy? The KeysView subtype, or the mapping?

repr(list), repr(dict) and repr(set) all render their full content in the 
result, no?

repr() on a list of 1 million of items *will* render all items, even if nobody 
wants to read such very long string :-)

If you want to get a smarter __repr__() than the default implementation: just 
override __repr__(), no?

I don't see why KeysView must be special.

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[issue32300] print(os.environ.keys()) should only print the keys

[Aaron Meurer]

Aaron Meurer  added the comment:

So the best fix is to just override keys() in the _Environ class, so that it 
returns an EnvironKeysView class that overrides __repr__?

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[issue32300] print(os.environ.keys()) should only print the keys

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

Don't make KeysView.__repr__ and ValuesView.__repr__ containing the lists of 
all keys and values. This will make the repr of the view of a mapping which is 
a proxy of an external DB containing the full content of that DB, which can be 
gigabytes. See for example rejected issue21670.

--
nosy: +serhiy.storchaka

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[issue32300] print(os.environ.keys()) should only print the keys

[STINNER Victor]

STINNER Victor  added the comment:

Cheryl: would you like to work on a PR? If yes, tests are needed.

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[issue32300] print(os.environ.keys()) should only print the keys

[R. David Murray]

R. David Murray  added the comment:

Agreed about the other classes if we change this.  Your solution looks 
reasonable to me.

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[issue32300] print(os.environ.keys()) should only print the keys

[STINNER Victor]

STINNER Victor  added the comment:

If we decide to change abc.KeysView.__repr__, IMHO we should also modify 
abc.ValuesView.__repr__, and maybe also abc.ItemsView.__repr__.

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[issue32300] print(os.environ.keys()) should only print the keys

[STINNER Victor]

STINNER Victor  added the comment:

Usually, I use print(sorted(os.environ)) since I prefer a sorted list and it 
prevents such issue :-)

David:
> I agree that the result is surprising, but there may not be a generic fix.

What about something like:

vstinner@apu$ ./python -c 'import os; print(os.environ.keys())'


vstinner@apu$ git diff
diff --git a/Lib/_collections_abc.py b/Lib/_collections_abc.py
index a5c7bfcda1..5e524dffbf 100644
--- a/Lib/_collections_abc.py
+++ b/Lib/_collections_abc.py
@@ -719,6 +719,9 @@ class KeysView(MappingView, Set):
 def __iter__(self):
 yield from self._mapping
 
+def __repr__(self):
+return '' % list(self)
+
 KeysView.register(dict_keys)
 
 

list(key_view) is valid. I mimicked dict views implementation:

static PyObject *
dictview_repr(_PyDictViewObject *dv)
{
PyObject *seq;
PyObject *result;

seq = PySequence_List((PyObject *)dv);
if (seq == NULL)
return NULL;

result = PyUnicode_FromFormat("%s(%R)", Py_TYPE(dv)->tp_name, seq);
Py_DECREF(seq);
return result;
}

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[issue32300] print(os.environ.keys()) should only print the keys

[R. David Murray]

Change by R. David Murray :


--
nosy: +csabella

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[issue32300] print(os.environ.keys()) should only print the keys

[R. David Murray]

R. David Murray  added the comment:

This is a consequence of the repr used by KeysView, which it inherits from 
MappingView.  I agree that the result is surprising, but there may not be a 
generic fix.  It's not entirely clear what KeysView should do here, but 
presumably we could at least add a repr to environ's use of it that would 
produce something useful.

Note that a workaround when doing something like a travis debug is to print 
os.environ._data.keys(), which will print the bytes versions of the keys.  I 
wouldn't recommend depending on that continuing to, though ;)

--
nosy: +r.david.murray, rhettinger, vstinner -csabella
type: behavior -> 
versions:  -Python 3.6

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[issue32300] print(os.environ.keys()) should only print the keys

[Cheryl Sabella]

Change by Cheryl Sabella :


--
components: +Library (Lib)
type:  -> behavior

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[issue32300] print(os.environ.keys()) should only print the keys

[Cheryl Sabella]

Cheryl Sabella  added the comment:

For your current situation, list(os.environ) or iter(os.environ) both return 
keys only.

It looks like the __repr__ on the class for os.environ is printed for 
os.environ (which is expected).  For os.environ.keys(), the same __repr__ is 
wrapped as a KeysView, for os.environ.values(), it's wrapped as a ValuesView, 
and os.environ.items(), as an ItemsView.

In 2.7, os.environ.keys() print just keys.

--
nosy: +csabella
versions: +Python 3.6

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[issue32300] print(os.environ.keys()) should only print the keys

[Aaron Meurer]

New submission from Aaron Meurer :

Take the following scenario which happened to me recently. I am trying to debug 
an issue on Travis CI involving environment variables. Basically, I am not sure 
if an environment variable is being set correctly. So in my code, I put

print(os.environ.keys())

The reason I put keys() was 1, I didn't care about the values, and 2, I have 
secure environment variables set on Travis. 

To my surprise, in the Travis logs, I found something like this

KeysView(environ({'TRAVIS_STACK_FEATURES': 'basic cassandra chromium couchdb 
disabled-ipv6 docker docker-compose elasticsearch firefox go-toolchain 
google-chrome jdk memcached mongodb mysql neo4j nodejs_interpreter 
perl_interpreter perlbrew phantomjs postgresql python_interpreter rabbitmq 
redis riak ruby_interpreter sqlite xserver', 'CI': 'true', ..., 'MANPATH': 
'/home/travis/.nvm/versions/node/v7.4.0/share/man:/home/travis/.kiex/elixirs/elixir-1.4.5/man:/home/travis/.rvm/rubies/ruby-2.4.1/share/man:/usr/local/man:/usr/local/clang-3.9.0/share/man:/usr/local/share/man:/usr/share/man:/home/travis/.rvm/man'}))

So instead of just printing the keys like I asked for, it printed the whole 
environment, plus "KeysView(environ(". Included here was my secure environment 
variable. 

Now, fortunately, Travis hides the contents of secure environment variables in 
the logs, but it didn't used to 
(https://blog.travis-ci.com/2017-05-08-security-advisory).

Aside from being a potential security issue, it's just annoying that it prints 
the whole environment. The values are much larger than the keys. With a normal 
dictionary, print(d.keys()) just prints the keys:

>>> print(dict(a=1, b=2).keys())
dict_keys(['a', 'b'])

--
messages: 308190
nosy: Aaron.Meurer
priority: normal
severity: normal
status: open
title: print(os.environ.keys()) should only print the keys
versions: Python 3.7

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