CODEWITHSUNDEEP
regexpython-3.x
user252046
user252046

Reputation: 407

re search cannot find hex bytes with letters [python 3.6]

pattern = b'\x08\x00\x2a\x00'
re.search(b'\x08', pattern).end()
>> 1

re.search(b'\x2a',pattern).end()
>> error: nothing to repeat at position 0

I am trying to search for a byte pattern in a dicom file, if it includes a hex value a-f, it gets an error.

Using str.find seems to work, but I was wondering if there is a way to make re serch work as well

Upvotes: 1

Views: 212

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 627292

The '\x2a' is an escape sequence that represents a * char. It is a quantifier that repeats the preceding pattern 0 or more times. You want to match a * char, so you may either tell the regex engine to search for an escaped *, b'\\\x2a', a regular string literal that represents a \* literal string, or use a hex entity with a regex escape, rb'\x2a', a raw string literal that repesents a literal \x2a string.

print(re.search(rb'\x2a',b'\x08\x00\x2a\x00').end())  # => 3
print(re.search(b'\\\x2a',b'\x08\x00\x2a\x00').end()) # => 3

See the Python 3 demo.

Upvotes: 3

Related Questions