contextlibredirectstderr

Contextlib.redirect_stderr is a context manager in the Python standard library that temporarily redirects writes to the interpreter’s standard error stream (sys.stderr) to another file-like object. It is provided by the contextlib module as redirect_stderr and is commonly used to capture or silence error output within a specific block of code.

The mechanism works by saving the current sys.stderr and replacing it with the specified target for the duration of the with block. When the block exits, the original sys.stderr is restored, even if an exception occurs inside the block. The redirection applies to all writes to sys.stderr made within the block, making it useful for logging, testing, or preventing noisy error messages from leaking to the console.

Parameters for redirect_stderr include a single argument: the new_target, which must be a file-like object that implements a write method (and typically a flush method). Examples of suitable targets include an open file object, an io.StringIO buffer, or a custom object with a write(string) method.

Example usage:

with redirect_stderr(open('errors.log', 'w')):

print('this goes to standard error', file=sys.stderr)

Note that, like other global streams in Python, this redirection affects the current process and is not isolated to a single thread. Nested redirections are supported, with inner blocks restoring their own previous target upon exit. See also redirect_stdout for parallel functionality on sys.stdout.

See also: contextlib.redirect_stdout.