file detection

[Skaperen]

you can detect if x is a float like:

if isinstance(x,float):
    ...

so how do you detect if x is a file?

[buran]

isinstance(x, file)

[snippsat]

file is no longer a built-in functions for Python 3.x.
This work Python 2.7 and 3.6.

>>> from io import IOBase

>>> f = open('hello.txt')
>>> isinstance(f, IOBase)
True

But remember type checking is really not good at all in Pythons,so use it sparse.

EAFP(Easier to ask for forgiveness than permission).

So let error occur then can catch it with try except.

LBYL(Look before you leap) check type before error occur,like in language like C/C++.

[metulburr]

if you have the path you can check with os.path.isfile

[Skaperen]

i want to check if what is passed to a function in stdout= is a file or file descriptor.  for file descriptor, checking for int is good enough.  but assuming whatever is not int is a file i think is not good enough ... something might succeed with something else.  i want an explicit test.  right now i am checking if 'fileno' in stdout.  i want this to work in the widest range of python versions as possible but at least 2.6-2.7 and 3.3-.

[micseydel]

but assuming whatever is not int is a file i think is not good enough ... something might succeed with something else.

Why is that not good enough? If it quacks like a duck, treat it like a duck. If it doesn't quack, then just raise an exception.

I also don't understand what you mean about file descriptors. That sounds like C-talk. In Python, it's an object, not a numeric.

[Skaperen]

I also don't understand what you mean about file descriptors. That sounds like C-talk. In Python, it's an object, not a numeric.

as in os.pipe()  ... how i connect 2 or more processes together in a command pipeline.

[nilamo]

Just ask nicely if it's a file?

>>> import os
>>> os.path.isfile("test.db")
True
>>> os.path.isfile("pipe://4433828") #...or whatever
False

[Larz60+]

File vs file descriptor is needed in C, when you have to deal with file handles.
I have never cared in python, and it hasn't hurt me yet.
If you want strict type checking then you should go back to programming in C.

[wavic]

In [1]: import os.path

In [2]: with open('39768.txt', 'r') as f:
   ...:     print(os.path.isfile(f.fileno()))
   ...:     
True