Why Should `sys.setdefaultencoding(\'utf-8\')` Not Be Used in Python 3?

Sys.setdefaultencoding("utf-8") Revisited: Why It Should Not Be Used in Python Scripts

In Python scripts, it is often seen that sys.setdefaultencoding("utf-8") is used at the beginning to switch the default ASCII encoding to UTF-8. However, this practice is strongly discouraged and has become obsolete in Python 3.

Reasons to Avoid Using sys.setdefaultencoding("utf-8")

As per the official Python documentation:

• It is only available during Python startup and should be called from a system-wide module (e.g., sitecustomize.py), which is accessed before Python runtime.
• After sitecustomize.py is evaluated, the sys.setdefaultencoding() function is removed from the sys module, making it inaccessible.
• To access it after startup, a reload hack is required, which is not recommended.

Consequences of Using sys.setdefaultencoding("utf-8")

• Potentially Inconsistent Behavior: It can lead to unexpected behavior as it might conflict with other encoding settings set later in the script.
• Performance Degradation: Reloading a system-wide module can significantly impact performance.
• Deprecation in Python 3: This function has been marked as obsolete in Python 3 and raising an error if called, indicating that it should not be used.

Recommended Solution

In Python 3, the default encoding is hard-wired to UTF-8, making sys.setdefaultencoding() redundant. Instead, it is advisable to use Unicode and encoding functions such as str.encode("utf-8") to explicitly convert strings to and from specific encodings.

References for Further Reading

• [Illusive sys.setdefaultencoding](http://blog.ianbicking.org/illusive-setdefaultencoding.html)
• [Printing Unicode from Python](http://nedbatchelder.com/blog/200401/printing_unicode_from_python.html)
• [One Ring to Rule Them All: Unicode](http://www.diveintopython3.net/strings.html#one-ring-to-rule-them-all)
• [All About Python and Unicode](http://boodebr.org/main/python/all-about-python-and-unicode)
• [Getting Unicode Right in Python](http://blog.notdot.net/2010/07/Getting-unicode-right-in-Python)

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