What's the More Pythonic Way to Convert a String to Bytes in Python 3?

Best Way to Convert String to Bytes in Python 3: Explained

Python 3 raises a TypeError when attempting to convert a string to bytes directly due to the string not supporting the buffer interface. This error message prompts the question: which of the following methods is more Pythonic?

b = bytes(mystring, 'utf-8')
b = mystring.encode('utf-8')

Exploration of the Bytes Constructor

Examining the documentation for bytes reveals that it points to bytearray, which offers various options for initializing an array of bytes. Among these options, one stands out:

bytearray(source[, encoding[, errors]])

Here, if source is a string, the encoding and errors parameters must be provided, whereby bytearray() converts the string to bytes using str.encode().

Pythonic Considerations

While bytes offers broader functionality beyond string encoding, for the specific task of encoding a string, invoking some_string.encode(encoding) is considered more Pythonic. This is primarily due to its clarity and purposefulness, as it explicitly states the intent to "take this string and encode it with this encoding."

In contrast, bytes(some_string, encoding) lacks an explicit verb, making the intended operation less apparent.

Performance and Implementation

Analysis of the Python source code confirms that unicode_string.encode(encoding) internally calls PyUnicode_AsEncodedString, which is the same implementation as used by the bytes() constructor. Hence, there is no performance or efficiency difference between the two methods for string encoding.

Symmetry and Readability

Moreover, unicode_string.encode(encoding) pairs symmetrically with its inverse, byte_string.decode(encoding), providing a consistent and intuitive approach to converting between string and byte representations.

Therefore, it is concluded that mystring.encode('utf-8') is the more Pythonic and preferred method for converting a string to bytes in Python 3.

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