From b430399d41fa88e9040cd055e55cf9211bf63c61 Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <rhettinger@users.noreply.github.com>
Date: Thu, 15 Dec 2022 20:40:45 +0200
Subject: [PATCH] GH-100234: Set a default value for random.expovariate()
 (GH-100235)

---
 Doc/library/random.rst                                       | 5 ++++-
 Lib/random.py                                                | 2 +-
 Lib/test/test_random.py                                      | 1 +
 .../Library/2022-12-14-11-45-38.gh-issue-100234.kn6yWV.rst   | 2 ++
 4 files changed, 8 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2022-12-14-11-45-38.gh-issue-100234.kn6yWV.rst

diff --git a/Doc/library/random.rst b/Doc/library/random.rst
index 669204ba65b..d944518a790 100644
--- a/Doc/library/random.rst
+++ b/Doc/library/random.rst
@@ -320,7 +320,7 @@ be found in any statistics text.
    ``beta > 0``. Returned values range between 0 and 1.
 
 
-.. function:: expovariate(lambd)
+.. function:: expovariate(lambd = 1.0)
 
    Exponential distribution.  *lambd* is 1.0 divided by the desired
    mean.  It should be nonzero.  (The parameter would be called
@@ -328,6 +328,9 @@ be found in any statistics text.
    range from 0 to positive infinity if *lambd* is positive, and from
    negative infinity to 0 if *lambd* is negative.
 
+   .. versionchanged:: 3.12
+      Added the default value for ``lambd``.
+
 
 .. function:: gammavariate(alpha, beta)
 
diff --git a/Lib/random.py b/Lib/random.py
index c70294ee0cb..e60b7294b6d 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -577,7 +577,7 @@ class Random(_random.Random):
         """
         return _exp(self.normalvariate(mu, sigma))
 
-    def expovariate(self, lambd):
+    def expovariate(self, lambd=1.0):
         """Exponential distribution.
 
         lambd is 1.0 divided by the desired mean.  It should be
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
index 1e825c3572d..67de54c7db8 100644
--- a/Lib/test/test_random.py
+++ b/Lib/test/test_random.py
@@ -988,6 +988,7 @@ class TestDistributions(unittest.TestCase):
         g.random = x[:].pop; g.uniform(1,10)
         g.random = x[:].pop; g.paretovariate(1.0)
         g.random = x[:].pop; g.expovariate(1.0)
+        g.random = x[:].pop; g.expovariate()
         g.random = x[:].pop; g.weibullvariate(1.0, 1.0)
         g.random = x[:].pop; g.vonmisesvariate(1.0, 1.0)
         g.random = x[:].pop; g.normalvariate(0.0, 1.0)
diff --git a/Misc/NEWS.d/next/Library/2022-12-14-11-45-38.gh-issue-100234.kn6yWV.rst b/Misc/NEWS.d/next/Library/2022-12-14-11-45-38.gh-issue-100234.kn6yWV.rst
new file mode 100644
index 00000000000..6d9b909d874
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-12-14-11-45-38.gh-issue-100234.kn6yWV.rst
@@ -0,0 +1,2 @@
+Set a default value of 1.0 for the ``lambd`` parameter in
+random.expovariate().