From: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
Date: Tue, 27 Jun 2023 00:47:55 +0000 (-0700)
Subject: Decrease cost of ipynb code path when unneeded (#3748)
X-Git-Url: https://git.madduck.net/etc/vim.git/commitdiff_plain/31b3b6701d2cfae072900f9d45dc8f1737ab282b

Decrease cost of ipynb code path when unneeded (#3748)

IPython is a very expensive import, like, at least 300ms. I'd also
venture that it's much more common than tokenize-rt, which is like 30ms.
I work in a repo where I use black, have IPython installed and there
happen to be a couple notebooks (that we don't want formatted). I know I
can force exclude ipynb, but this change doesn't really have a cost.
---

diff --git a/CHANGES.md b/CHANGES.md
index a9d4d9d..6fa0e4b 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -47,6 +47,8 @@
 
 <!-- Changes that improve Black's performance. -->
 
+- Avoid importing `IPython` in a case where we wouldn't need it (#3748)
+
 ### Output
 
 <!-- Changes to Black's terminal output and error messages -->
diff --git a/src/black/handle_ipynb_magics.py b/src/black/handle_ipynb_magics.py
index 9e1af75..2b6b920 100644
--- a/src/black/handle_ipynb_magics.py
+++ b/src/black/handle_ipynb_magics.py
@@ -58,8 +58,13 @@ class Replacement:
 @lru_cache()
 def jupyter_dependencies_are_installed(*, verbose: bool, quiet: bool) -> bool:
     try:
-        import IPython  # noqa:F401
+        # isort: off
+        # tokenize_rt is less commonly installed than IPython
+        # and IPython is expensive to import
         import tokenize_rt  # noqa:F401
+        import IPython  # noqa:F401
+
+        # isort: on
     except ModuleNotFoundError:
         if verbose or not quiet:
             msg = (