Python - verify a PNG file and get image dimensions

useful snippet for getting .png image dimensions without using an external imaging library.

#!/usr/bin/env python

import struct


def get_image_info(data):
    if is_png(data):
        w, h = struct.unpack('>LL', data[16:24])
        width = int(w)
        height = int(h)
    else:
        raise Exception('not a png image')
    return width, height


def is_png(data):
    return (data[:8] == '\211PNG\r\n\032\n'and (data[12:16] == 'IHDR'))


if __name__ == '__main__':
    with open('foo.png', 'rb') as f:
        data = f.read()

    print is_png(data)
    print get_image_info(data)

/headnods:
getimageinfo.py source, Portable_Network_Graphics (Wikipedia)

Python Unit Testing Tutorial (PyMOTW unittest update)

tl;dr: an update to PyMOTW for `unittest` in Python 3: Python Unit Testing Tutorial.

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When I was learning programming in Python, Doug Hellmann's 'PyMOTW' (Python Module Of The Week) blog-series was one of the best resources to learn Python's standard library.

His series later culminated in the book: 'The Python Standard Library By Example'.

The PyMOTW entry on `unittest` was a great introduction to unit testing in Python. Since the PyMOTW version is getting quite outdated, I updated the `unittest` module entry.

This new version includes some edits and updates to the text, and all code and examples have been updated to reflect Python 3.3.

Have a look at my updated Python 3.3 version:
'Python Unit Testing Tutorial'

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license: Creative Commons Attribution, Non-commercial, Share-alike 3.0

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say no to bugs...

Python - "The Matrix" in your terminal

Linux console program in Python, that scrolls binary numbers vertically in your terminal. Inspired by the movie: The Matrix

a screenshot:

in action:

the Code:

	""""Create "The Matrix" of binary numbers scrolling vertically in your terminal.
	original code adapted from juancarlospaco:
	- http://ubuntuforums.org/showpost.php?p=10306676
	Inspired by the movie: The Matrix
	- Corey Goldberg (2013)
	Requires:
	- Linux
	- Python 2.7 or 3+
	"""
	import fcntl
	import time
	import random
	import struct
	import sys
	import termios
	class message(str):
	def __new__(cls, text, speed):
	self = super(message, cls).__new__(cls, text)
	self.speed = speed
	self.y = -1 * len(text)
	self.x = random.randint(0, display().width)
	self.skip = 0
	return self
	def move(self):
	if self.speed > self.skip:
	self.skip += 1
	else:
	self.skip = 0
	self.y += 1
	class display(list):
	def __init__(self):
	self.height, self.width = struct.unpack('hh', fcntl.ioctl(1, termios.TIOCGWINSZ, '1234'))
	self[:] = [' ' for y in range(self.height) for x in range(self.width)]
	def set_vertical(self, x, y, string):
	string = string[::-1]
	if x < 0:
	x = 80 + x
	if x >= self.width:
	x = self.width - 1
	if y < 0:
	string = string[abs(y):]
	y = 0
	if y + len(string) > self.height:
	string = string[0:self.height - y]
	if y >= self.height:
	return
	start = y * self.width + x
	length = self.width * (y + len(string))
	step = self.width
	self[start:length:step] = string
	def __str__(self):
	return ''.join(self)
	def matrix(iterations, sleep_time=.08):
	messages = []
	d = display()
	for _ in range(iterations):
	messages.append(message('10' * 16, random.randint(1, 5)))
	for text in messages:
	d.set_vertical(text.x, text.y, text)
	text.move()
	sys.stdout.write('\033[1m\033[32m%s\033[0m\r' % d)
	sys.stdout.flush()
	time.sleep(sleep_time)
	if __name__ == '__main__':
	while True:
	try:
	matrix(150)
	except KeyboardInterrupt:
	sys.stdout.write('\n\033[1m\033[32m=== Matrix Stopped ====\033[0m\n')
	sys.exit()

view raw matrix_terminal_python.py hosted with ❤ by GitHub

https://gist.github.com/4530348

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Python Testing - PhantomJS with Selenium WebDriver

PhantomJS is a headless WebKit with JavaScript API. It can be used for headless website testing.

PhantomJS has a lot of different uses. The interesting bit for me is to use PhantomJS as a lighter-weight replacement for a browser when running web acceptance tests. This enables faster testing, without a display or the overhead of full-browser startup/shutdown.

I write my web automation using Selenium WebDriver, in Python.

In future versions of PhantomJS, the GhostDriver component will be included.

GhostDriver is a pure JavaScript implementation of the WebDriver Wire Protocol for PhantomJS. It's a Remote WebDriver that uses PhantomJS as back-end.

So, Ghostdriver is the bridge we need to use Selenium WebDriver with Phantom.JS.

Since it is not available in the current PhantomJS release, you can try it yourself by compiling a special version of PhantomJS:

It wes pretty trvial to setup on Ubuntu (12.04):

$ sudo apt-get install build-essential chrpath git-core libssl-dev libfontconfig1-dev
$ git clone git://github.com/ariya/phantomjs.git
$ cd phantomjs
$ git checkout 1.8
$ ./build.sh
$ git remote add detro https://github.com/detro/phantomjs.git
$ git fetch detro && git checkout -b detro-ghostdriver-dev remotes/detro/ghostdriver-dev
$ ./build.sh

Then grab the `phantomjs` binary it produced (look inside `phantomjs/bin`). This is a self-contained executable, it can be moved to a different directory or another machine. Make sure it is located somewhere on your PATH, or declare it's location when creating your PhantomJS driver like the example below.

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for these examples, `phantomjs` binary is located in same directory as test script.

Example: Python Using PhantomJS and Selenium WebDriver.

#!/usr/bin/env python

driver = webdriver.PhantomJS('./phantomjs')
# do webdriver stuff here
driver.quit()

Example: Python Unit Test Using PhantomJS and Selenium WebDriver.

#!/usr/bin/env python

import unittest
from selenium import webdriver


class TestUbuntuHomepage(unittest.TestCase):
    
    def setUp(self):
        self.driver = webdriver.PhantomJS('./phantomjs')
        
    def testTitle(self):
        self.driver.get('http://www.ubuntu.com/')
        self.assertIn('Ubuntu', self.driver.title)
        
    def tearDown(self):
        self.driver.quit()


if __name__ == '__main__':
    unittest.main(verbosity=2)

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resources:

• http://phantomjs.org/build.html
• https://github.com/detro/ghostdriver
• Selenium WebDriver Python API Documentation