PyTesseract is an in-development python package for OCR.

Using PyTesseract is pretty easy:

try:
    import Image
except ImportError:
    from PIL import Image

import pytesseract

    #Basic OCR
    print(pytesseract.image_to_string(Image.open('test.png')))

    #In French
    print(pytesseract.image_to_string(Image.open('test-european.jpg'), lang='fra’))

PyTesseract is open source and can be found here.

Another module of some use is PyOCR, source code of which is here.

Also simple to use and has more features than PyTesseract.

To initialize:

from PIL import Image
import sys

import pyocr
import pyocr.builders

tools = pyocr.get_available_tools()
# The tools are returned in the recommended order of usage
tool = tools[0]

langs = tool.get_available_languages()
lang = langs[0]
# Note that languages are NOT sorted in any way. Please refer
# to the system locale settings for the default language
# to use.

And some examples of usage:

txt = tool.image_to_string(
    Image.open('test.png'),
    lang=lang,
    builder=pyocr.builders.TextBuilder()
)
# txt is a Python string

word_boxes = tool.image_to_string(
    Image.open('test.png'),
    lang="eng",
    builder=pyocr.builders.WordBoxBuilder()
)
# list of box objects. For each box object:
#   box.content is the word in the box
#   box.position is its position on the page (in pixels)
#
# Beware that some OCR tools (Tesseract for instance)
# may return empty boxes

line_and_word_boxes = tool.image_to_string(
    Image.open('test.png'), lang="fra",
    builder=pyocr.builders.LineBoxBuilder()
)
# list of line objects. For each line object:
#   line.word_boxes is a list of word boxes (the individual words in the line)
#   line.content is the whole text of the line
#   line.position is the position of the whole line on the page (in pixels)
#
# Beware that some OCR tools (Tesseract for instance)
# may return empty boxes

# Digits - Only Tesseract (not 'libtesseract' yet !)
digits = tool.image_to_string(
    Image.open('test-digits.png'),
    lang=lang,
    builder=pyocr.tesseract.DigitBuilder()
)
# digits is a python string