Python Context Manager: Difference between revisions
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=How it Works= | =How it Works= | ||
When the interpreter encounters the <code>[[Python_Language | When the interpreter encounters the <code>[[Python_Language#with|with]]</code> statement, it creates a new context. | ||
The context an optionally return an object, which is accessible from the indented block that follows <code>with</code>. | The context an optionally return an object, which is accessible from the indented block that follows <code>with</code>. |
Revision as of 00:23, 29 August 2022
External
Internal
Overview
An execution context is useful when the code uses resources that need closing, even if the code follows an unexpected execution path, like when an exception is raised.
An execution context is equivalent with the following construct:
r = Resource()
r.open()
try:
#
# use resource, while anywhere in this code block exception might be thrown
#
finally:
r.close()
The equivalent semantics using a context manager can be achieved with this syntax:
with <create-context> as ctx:
#
# use the context
#
#
# at the exit from the indented block, the context is automatically cleaned up
#
How it Works
When the interpreter encounters the with
statement, it creates a new context.
The context an optionally return an object, which is accessible from the indented block that follows with
.