gh-73965: New environment variable PYTHON_HISTORY (#13208)

It can be used to set the location of a .python_history file

---------

Co-authored-by: Levi Sabah <0xl3vi@gmail.com>
Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>

Doc/using/cmdline.rst

@@ -1139,6 +1139,14 @@ conflict.
 
    .. versionadded:: 3.13
 
+.. envvar:: PYTHON_HISTORY
+
+   This environment variable can be used to set the location of a
+   ``.python_history`` file (by default, it is ``.python_history`` in the
+   user's home directory).
+
+   .. versionadded:: 3.13
+
 Debug-mode variables
 ~~~~~~~~~~~~~~~~~~~~
 

Doc/whatsnew/3.13.rst

@@ -132,6 +132,11 @@ Other Language Changes
   equivalent of the :option:`-X frozen_modules <-X>` command-line option.
   (Contributed by Yilei Yang in :gh:`111374`.)
 
+* The new :envvar:`PYTHON_HISTORY` environment variable can be used to change
+  the location of a ``.python_history`` file.
+  (Contributed by Levi Sabah, Zackery Spytz and Hugo van Kemenade in
+  :gh:`73965`.)
+
 New Modules
 ===========
 

Lib/site.py

@@ -433,6 +433,20 @@ def setcopyright():
 def sethelper():
     builtins.help = _sitebuiltins._Helper()
 
+
+def gethistoryfile():
+    """Check if the PYTHON_HISTORY environment variable is set and define
+    it as the .python_history file.  If PYTHON_HISTORY is not set, use the
+    default .python_history file.
+    """
+    if not sys.flags.ignore_environment:
+        history = os.environ.get("PYTHON_HISTORY")
+        if history:
+            return history
+    return os.path.join(os.path.expanduser('~'),
+        '.python_history')
+
+
 def enablerlcompleter():
     """Enable default readline configuration on interactive prompts, by
     registering a sys.__interactivehook__.
@@ -467,13 +481,13 @@ def register_readline():
             pass
 
         if readline.get_current_history_length() == 0:
-            # If no history was loaded, default to .python_history.
+            # If no history was loaded, default to .python_history,
+            # or PYTHON_HISTORY.
             # The guard is necessary to avoid doubling history size at
             # each interpreter exit when readline was already configured
             # through a PYTHONSTARTUP hook, see:
             # http://bugs.python.org/issue5845#msg198636
-            history = os.path.join(os.path.expanduser('~'),
-                                   '.python_history')
+            history = gethistoryfile()
             try:
                 readline.read_history_file(history)
             except OSError:

Lib/test/test_site.py

@@ -7,6 +7,7 @@
 import unittest
 import test.support
 from test import support
+from test.support.script_helper import assert_python_ok
 from test.support import os_helper
 from test.support import socket_helper
 from test.support import captured_stderr
@@ -338,6 +339,19 @@ def test_no_home_directory(self):
             mock_addsitedir.assert_not_called()
             self.assertFalse(known_paths)
 
+    def test_gethistoryfile(self):
+        filename = 'file'
+        rc, out, err = assert_python_ok('-c',
+            f'import site; assert site.gethistoryfile() == "{filename}"',
+            PYTHON_HISTORY=filename)
+        self.assertEqual(rc, 0)
+
+        # Check that PYTHON_HISTORY is ignored in isolated mode.
+        rc, out, err = assert_python_ok('-I', '-c',
+            f'import site; assert site.gethistoryfile() != "{filename}"',
+            PYTHON_HISTORY=filename)
+        self.assertEqual(rc, 0)
+
     def test_trace(self):
         message = "bla-bla-bla"
         for verbose, out in (True, message + "\n"), (False, ""):

Misc/NEWS.d/next/Library/2019-05-08-13-14-11.bpo-29779.jg33dp.rst

@@ -0,0 +1,2 @@
+Add a new :envvar:`PYTHON_HISTORY` environment variable to set the location
+of a ``.python_history`` file.

Misc/python.man

@@ -604,6 +604,9 @@ can be set to the callable of your debugger of choice.
 .IP PYTHON_COLORS
 If this variable is set to 1, the interpreter will colorize various kinds of
 output. Setting it to 0 deactivates this behavior.
+.IP PYTHON_HISTORY
+This environment variable can be used to set the location of a history file
+(on Unix, it is \fI~/.python_history\fP by default).
 .SS Debug-mode variables
 Setting these variables only has an effect in a debug build of Python, that is,
 if Python was configured with the

Python/initconfig.c

@@ -296,6 +296,7 @@ static const char usage_envvars[] =
 "PYTHON_COLORS           : If this variable is set to 1, the interpreter will"
 "   colorize various kinds of output. Setting it to 0 deactivates this behavior.\n"
 "These variables have equivalent command-line parameters (see --help for details):\n"
+"PYTHON_HISTORY: the location of a .python_history file.\n"
 "PYTHONDEBUG             : enable parser debug mode (-d)\n"
 "PYTHONDONTWRITEBYTECODE : don't write .pyc files (-B)\n"
 "PYTHONINSPECT           : inspect interactively after running script (-i)\n"