How do I get the ASCII value of a character as an int
in Python?
5 Answers
From here:
The function
ord()
gets the int value of the char. And in case you want to convert back after playing with the number, functionchr()
does the trick.
>>> ord('a')
97
>>> chr(97)
'a'
>>> chr(ord('a') + 3)
'd'
>>>
In Python 2, there was also the unichr
function, returning the Unicode character whose ordinal is the unichr
argument:
>>> unichr(97)
u'a'
>>> unichr(1234)
u'\u04d2'
In Python 3 you can use chr
instead of unichr
.
Note that ord()
doesn't give you the ASCII value per se; it gives you the numeric value of the character in whatever encoding it's in. Therefore the result of ord('ä')
can be 228 if you're using Latin-1, or it can raise a TypeError
if you're using UTF-8. It can even return the Unicode codepoint instead if you pass it a unicode:
>>> ord(u'あ')
12354
The accepted answer is correct, but there is a more clever/efficient way to do this if you need to convert a whole bunch of ASCII characters to their ASCII codes at once. Instead of doing:
for ch in mystr:
code = ord(ch)
or the slightly faster:
for code in map(ord, mystr):
you convert to Python native types that iterate the codes directly. On Python 3, it's trivial:
for code in mystr.encode('ascii'):
and on Python 2.6/2.7, it's only slightly more involved because it doesn't have a Py3 style bytes
object (bytes
is an alias for str
, which iterates by character), but they do have bytearray
:
# If mystr is definitely str, not unicode
for code in bytearray(mystr):
# If mystr could be either str or unicode
for code in bytearray(mystr, 'ascii'):
Encoding as a type that natively iterates by ordinal means the conversion goes much faster; in local tests on both Py2.7 and Py3.5, iterating a str
to get its ASCII codes using map(ord, mystr)
starts off taking about twice as long for a len
10 str
than using bytearray(mystr)
on Py2 or mystr.encode('ascii')
on Py3, and as the str
gets longer, the multiplier paid for map(ord, mystr)
rises to ~6.5x-7x.
The only downside is that the conversion is all at once, so your first result might take a little longer, and a truly enormous str
would have a proportionately large temporary bytes
/bytearray
, but unless this forces you into page thrashing, this isn't likely to matter.