How to get the ASCII value of a character

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, function chr() 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.

ord() - Python 3.6.5rc1 documentation

ord() - Python 2.7.14 documentation

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

You are looking for:

ord()

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.