Python3 open(), read(), or write()doesn't check argument type before action causing a hang.  Would like to catch exceptions but not without an exception to return.  See below.

Python3.6:
Python 3.6.0 (default, Dec 24 2016, 08:01:42)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> test = False
>>> with open(str(test)) as f:
...     fail = f.read()
...


python2.7:
╰─λ python2                                                                                                                                                                                     0 < 09:35:31
Python 2.7.13 (default, Dec 18 2016, 07:03:39)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> test = False
>>> with open(test) as f:
...     fail = f.read()
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: coercing to Unicode: need string or buffer, bool found

The first example raises an error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
FileNotFoundError: [Errno 2] No such file or directory: 'False'

Unless you have a file named "False" in the current directory of course.

What behavior you expected?

Serhiy,

I expected a type error or a filenotfound like you received, however mine doesn't return the same. It just hangs.  I've attached a picture.  Also, I meant this to be for 3.6 not 3.5.

>>> test = False
>>> with open(test) as f:
...     fail = f.read()
...

Builtin open() in Python 3 (and io.open() in Python 2.7) accept unicode strings, byte strings and integers as the first arguments (general path-like objects also are supported in Python 3.6, but it doesn't matter). bool is a subtype of int, and False is equal to integer 0. 0 is a file descriptor of sys.stdin.

>>> import sys
>>> sys.stdin.fileno()
0

Thus open(False) is equivalent to open(sys.stdin.fileno()). It creates a file object that wraps the file descriptor 0. This is legitimate operation.