Generate random UTF-8 string in Python

Question

I'd like to test the Unicode handling of my code. Is there anything I can put in random.choice() to select from the entire Unicode range, preferably not an external module? Neither Google nor StackOverflow seems to have an answer.

Edit: It looks like this is more complex than expected, so I'll rephrase the question - Is the following code sufficient to generate all valid non-control characters in Unicode?

unicode_glyphs = ''.join(
    unichr(char)
    for char in xrange(1114112) # 0x10ffff + 1
    if unicodedata.category(unichr(char))[0] in ('LMNPSZ')
    )

Answer 1

Since Unicode is just a range of - well - codes, what about using unichr() to get the unicode string corresponding to a random number between 0 and 0xFFFF?
(Of course that would give just one codepoint, so iterate as required)

Answer 2

You could download a website written in greek or german that uses unicode and feed that to your code.

Answer 3

There is a UTF-8 stress test from Markus Kuhn you could use.

See also Really Good, Bad UTF-8 example test data.

Answer 4

It depends how thoroughly you want to do the testing and how accurately you want to do the generation. In full, Unicode is a 21-bit code set (U+0000 .. U+10FFFF). However, some quite large chunks of that range are set aside for custom characters. Do you want to worry about generating combining characters at the start of a string (because they should only appear after another character)?

The basic approach I'd adopt is randomly generate a Unicode code point (say U+2397 or U+31232), validate it in context (is it a legitimate character; can it appear here in the string) and encode valid code points in UTF-8.

If you just want to check whether your code handles malformed UTF-8 correctly, you can use much simpler generation schemes.

Note that you need to know what to expect given the input - otherwise you are not testing; you are experimenting.

Answer 5

Here is an example function that probably creates a random well-formed UTF-8 sequence, as defined in Table 3–7 of Unicode 5.0.0:

#!/usr/bin/env python3.1

# From Table 3–7 of the Unicode Standard 5.0.0

import random

def byte_range(first, last):
    return list(range(first, last+1))

first_values = byte_range(0x00, 0x7F) + byte_range(0xC2, 0xF4)
trailing_values = byte_range(0x80, 0xBF)

def random_utf8_seq():
    first = random.choice(first_values)
    if first <= 0x7F:
        return bytes([first])
    elif first <= 0xDF:
        return bytes([first, random.choice(trailing_values)])
    elif first == 0xE0:
        return bytes([first, random.choice(byte_range(0xA0, 0xBF)), random.choice(trailing_values)])
    elif first == 0xED:
        return bytes([first, random.choice(byte_range(0x80, 0x9F)), random.choice(trailing_values)])
    elif first <= 0xEF:
        return bytes([first, random.choice(trailing_values), random.choice(trailing_values)])
    elif first == 0xF0:
        return bytes([first, random.choice(byte_range(0x90, 0xBF)), random.choice(trailing_values), random.choice(trailing_values)])
    elif first <= 0xF3:
        return bytes([first, random.choice(trailing_values), random.choice(trailing_values), random.choice(trailing_values)])
    elif first == 0xF4:
        return bytes([first, random.choice(byte_range(0x80, 0x8F)), random.choice(trailing_values), random.choice(trailing_values)])

print("".join(str(random_utf8_seq(), "utf8") for i in range(10)))

Because of the vastness of the Unicode standard I cannot test this thoroughly. Also note that the characters are not equally distributed (but each byte in the sequence is).

Answer 6

Answering revised question:

Yes, on a strict definition of "control characters" -- note that you won't include CR, LF, and TAB; is that what you want?

Please consider responding to my earlier invitation to tell us what you are really trying to do.