bpo-13041: Use shutil.get_terminal_size() in argparse.HelpFormatter (GH-8459)

Author: berkerpeksag

Lib/argparse.py

@@ -85,6 +85,7 @@
 
 import os as _os
 import re as _re
+import shutil as _shutil
 import sys as _sys
 
 from gettext import gettext as _, ngettext
@@ -164,10 +165,7 @@ def __init__(self,
 
  # default setting for width
  if width is None:
- try:
- width = int(_os.environ['COLUMNS'])
- except (KeyError, ValueError):
- width = 80
+ width = _shutil.get_terminal_size().columns
  width -= 2
 
  self._prog = prog

Lib/test/test_argparse.py

@@ -23,9 +23,9 @@ class TestCase(unittest.TestCase):
  def setUp(self):
  # The tests assume that line wrapping occurs at 80 columns, but this
  # behaviour can be overridden by setting the COLUMNS environment
- # variable. To ensure that this assumption is true, unset COLUMNS.
+ # variable. To ensure that this width is used, set COLUMNS to 80.
  env = support.EnvironmentVarGuard()
- env.unset("COLUMNS")
+ env['COLUMNS'] = '80'
  self.addCleanup(env.__exit__)
 
 
@@ -5122,6 +5122,7 @@ def test_all_exports_everything_but_modules(self):
 class TestWrappingMetavar(TestCase):
 
  def setUp(self):
+ super().setUp()
  self.parser = ErrorRaisingArgumentParser(
  'this_is_spammy_prog_with_a_long_name_sorry_about_the_name'
  )

Misc/NEWS.d/next/Library/2018-07-25-12-08-48.bpo-13041.lNmgDz.rst

@@ -0,0 +1,3 @@
+Use :func:`shutil.get_terminal_size` to calculate the terminal width
+correctly in the ``argparse.HelpFormatter`` class. Initial patch by Zbyszek
+Jędrzejewski-Szmek.