Issue #15767: Introduce ModuleNotFoundError, a subclass of
ImportError.
The exception is raised by import when a module could not be found.
Technically this is defined as no viable loader could be found for the
specified module. This includes ``from ... import`` statements so that
the module usage is consistent for all situations where import
couldn't find what was requested.
This should allow for the common idiom of::
try:
import something
except ImportError:
pass
to be updated to using ModuleNotFoundError and not accidentally mask
ImportError messages that should propagate (e.g. issues with a
loader).
This work was driven by the fact that the ``from ... import``
statement needed to be able to tell the difference between an
ImportError that simply couldn't find a module (and thus silence the
exception so that ceval can raise it) and an ImportError that
represented an actual problem.
diff --git a/Doc/c-api/exceptions.rst b/Doc/c-api/exceptions.rst
index c0c30a0..1bdcdd3 100644
--- a/Doc/c-api/exceptions.rst
+++ b/Doc/c-api/exceptions.rst
@@ -686,6 +686,8 @@
+-----------------------------------------+---------------------------------+----------+
| :c:data:`PyExc_ImportError` | :exc:`ImportError` | |
+-----------------------------------------+---------------------------------+----------+
+| :c:data:`PyExc_ModuleNotFoundError` | :exc:`ModuleNotFoundError` | |
++-----------------------------------------+---------------------------------+----------+
| :c:data:`PyExc_IndexError` | :exc:`IndexError` | |
+-----------------------------------------+---------------------------------+----------+
| :c:data:`PyExc_InterruptedError` | :exc:`InterruptedError` | |
diff --git a/Doc/library/exceptions.rst b/Doc/library/exceptions.rst
index ece035d..933667c 100644
--- a/Doc/library/exceptions.rst
+++ b/Doc/library/exceptions.rst
@@ -169,8 +169,8 @@
.. exception:: ImportError
- Raised when an :keyword:`import` statement fails to find the module definition
- or when a ``from ... import`` fails to find a name that is to be imported.
+ Raised when the :keyword:`import` statement has troubles trying to load a
+ module.
The :attr:`name` and :attr:`path` attributes can be set using keyword-only
arguments to the constructor. When set they represent the name of the module
@@ -180,6 +180,15 @@
.. versionchanged:: 3.3
Added the :attr:`name` and :attr:`path` attributes.
+.. exception:: ModuleNotFoundError
+
+ A subclass of :exc:`ImportError` which is raised by :keyword:`import` when a
+ module could not be located. This includes ``from ... import`` statements as
+ the specific attribute being requested cannot be known a priori to be a module
+ or some other type of object.
+
+ .. versionadded:: 3.4
+
.. exception:: IndexError
diff --git a/Doc/whatsnew/3.4.rst b/Doc/whatsnew/3.4.rst
index 468ba1f..23ccae2 100644
--- a/Doc/whatsnew/3.4.rst
+++ b/Doc/whatsnew/3.4.rst
@@ -137,6 +137,9 @@
* Unicode database updated to UCD version 6.2.
+* Import now raises the new exception :exc:`ModuleNotFoundError` (subclass of
+ :exc:`ImportError`) when it cannot find something.
+
New Modules