Thoughts of a programmer

Python 3 and Unicode

If you don’t know what is Unicode, UTF-8 or UTF-16 or if need to refresh your memory on these topics, then before reading this article, check this one What everyone should know about Unicode.

I have divided this article in two parts, one for Python 2 and one for Python 3, since there are some differences in how each handles string and unicode in general. You can either read both of them or read just for the language you are interested in. This article is for Python 3. For Python 2, check out this article.

Python 3 has two built-in types for handling strings. One is the str type and the other one is bytes. All the string literals that you normally create in your python program like

    str_type_string = 'Some random string'

are the str type string literals. These are also the unicode strings. There is no separate unicode type that we have in Python 2.

Other type is the bytes type. They are just a series of bytes. To create them, you would have to use b prefix, like

    bytes_string = b'\x45\x89'
    print type(bytes_string)

You would get the type of the string as bytes. These is the same as the str type that we have in Python 2. So, in a nutshell, if you are moving from Python 2 to Python 3, you would find that the normal str type is replaced by bytes type and the unicode type is replaced by the str type.

To use unicode characters in Python 3, you have several options-

    unicode_string_literal = 'omega\u03a9'

This would give you a str type string.

    bytes_type_string = b'\xce\xa9'
    unicode_string = str(bytes_type_string, encoding='utf8')

The encoding argument specifies the encoding of the input string given as argument to the str function. Here, I am passing ‘utf8’ as I am using \xce\xa9 which is the utf-8 encoding for the Ω character. str function would give decoded unicode string.

    bytes_type_string = 'omega\xce\xa9'
    unicode_string = bytes_type_string.decode('utf8')

Finally to convert the unicode string into bytes type, use the decode counterpart function encode.

    unicode_string = u'\u03a9'
    bytes_string = unicode_string.encode('utf16')

Just pass in the encoding and it will give you the encoded byte string. On my machine it gave the ouput


\xfe\xff is the BOM character followed by the utf-16 encoding of the Ω character \x03\xa9, but in the reverse order since my machine is a little-endian machine. You may get different result on your machine depending upon your machine endianess.

Working with unicode in files

Now suppose, you want to read in a file which is encoded using UTF-8 or UTF-16. Unlike Python 2, where you have to use the codecs module open function to handle the unicode files, in Python 3, you can use the system’s normal open function. This function accepts an encoding of the file as an argument and would automatically convert the encoded bytes from the file to the unicode characters for you.

    unicode_file = 'unicode_test.txt'
    with open(unicode_file, mode='r', encoding='utf-8') as file:
        unicode_string =

Similary, you can use the file.write() function to write a unicode string to a file and the function will internally convert your string into the proper series of bytes and write to the disk.

General Strategy in working with Unicode

Generally when you have to work with Unicode, what you can do is accept the input from any source, it may be from the user, from a network, from a file, in any encoding, and convert all the data into unicode internally. Then you can safely work on that unicode data, because you know that all the data is in the same format. When the times comes to write or send the data, then convert it back to the original encoding.

Thank you for reading my article. Let me know if you liked my article or any other suggestions for me, in the comments section below. And please, feel free to share :)