How to get the ASCII value of a character?

问题:

How do I get the ASCII value of a character as an int in Python?

回答1:

From here:

function ord() would get the int value of the char. And in case you want to convert back after playing with the number, function chr() does the trick.

>>> ord(\'a\')
97
>>> chr(97)
\'a\'
>>> chr(ord(\'a\') + 3)
\'d\'
>>>

In Python 2, there is 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.

---

ord() - Python 3.6.5rc1 documentation

ord() - Python 2.7.14 documentation

回答2:

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

回答3:

You are looking for:

ord()

回答4:

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.