如何检测控制台是否支持Python中的ANSI转义码？

Question

In order to detect if console, correctly sys.stderr or sys.stdout , I was doing the following test:

if hasattr(sys.stderr, "isatty") and sys.stderr.isatty():
   if platform.system()=='Windows':
       # win code (ANSI not supported but there are alternatives)
   else:
       # use ANSI escapes
else:
   # no colors, usually this is when you redirect the output to a file

Now the problem became more complex while running this Python code via an IDE (like PyCharm). Recently PyCharm added support for ANSI, but the first test fails: it has the isatty attribute but it is set to False .

I want to modify the logic so it will properly detect if the output supports ANSI coloring. One requirement is that under no circumstance I should output something out when the output is redirected to a file (for console it would be acceptable).

Update

Added more complex ANSI test script at https://gist.github.com/1316877

Answer 1

Django users can use django.core.management.color.supports_color function.

if supports_color():
    ...

The code they use is:

def supports_color():
    """
    Returns True if the running system's terminal supports color, and False
    otherwise.
    """
    plat = sys.platform
    supported_platform = plat != 'Pocket PC' and (plat != 'win32' or
                                                  'ANSICON' in os.environ)
    # isatty is not always implemented, #6223.
    is_a_tty = hasattr(sys.stdout, 'isatty') and sys.stdout.isatty()
    return supported_platform and is_a_tty

See https://github.com/django/django/blob/master/django/core/management/color.py

Answer 2

I can tell you how others have solved this problem, but it's not pretty. If you look at ncurses as an example (which needs to be able to run on all kinds of different terminals), you'll see that they use a terminal capabilities database to store every kind of terminal and its capabilities. The point being, even they were never able to automatically "detect" these things.

I don't know if there's a cross-platform termcap, but it's probably worth your time to look for it. Even if it's out there though, it may not have your terminal listed and you may have to manually add it.