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Archive for the ‘python’ Category

extract e-mails from a file

October 10, 2017 Leave a comment

Problem
You have a text file and you want to extract all the e-mail addresses from it. For research purposes, of course.

Solution

#!/usr/bin/env python3

import re
import sys

def extract_emails_from(fname):
    with open(fname, errors='replace') as f:
        for line in f:
            match = re.findall(r'[\w\.-]+@[\w\.-]+', line)
            for e in match:
                if '?' not in e:
                    print(e)
                    
def main():
    fname = sys.argv[1]
    extract_emails_from(fname)

##############################################################################

if __name__ == "__main__":
    if len(sys.argv) == 1:
        print("Error: provide a text file!", file=sys.stderr)
        exit(1)
    # else
    main()

I had character encoding problems with some lines where the original program died with an exception. Using “open(fname, errors='replace')” will replace problematic characters with a “?“, hence the extra check before printing an e-mail to the screen.

The core of the script is the regex to find e-mails. That tip is from here.

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Categories: python Tags: , ,

visiting Finland

August 31, 2017 Leave a comment

Last week I gave a 2-day long intensive introductory Python course at the University of Jyväskylä, Finland. It went well :)

The course was for students who already learnt programming but never used Python before. We covered the following topics: introduction, strings, lists, loops, tuple data type, list comprehension, control structures, functions, set, dictionary, file handling. We also solved a lot of exercises. Total length of the course was 2 x 5 hours.

Categories: python Tags: , , ,

pythonz: install any Python version in your HOME folder

May 20, 2017 3 comments

Problem
You want to install an older / newer version of Python. You don’t want to install it systemwide since you don’t want to mess up your system. How to install it in your HOME folder?

Solution
pythonz was made to address this problem. Install it and add an extra line to your .bashrc (see the docs). Some useful commands:

$ pythonz update           # self-update
$ pythonz list             # list of installed Python versions
$ pythonz list -a          # list of available (installable) Python versions
$ pythonz install 3.5.3    # install CPython 3.5.3
$ pythonz locate 3.5.3     # Where is it installed?

Here is how to create a virtualenv using a specific Python version that was installed with pythonz:

$ virtualenv -p $(pythonz locate 3.5.3) ~/.virtualenvs/project_name

I have a project in a virtual environment that works well with Python 3.5 (Ubuntu). Howeverm, under Manjaro the default Python is 3.6 and the project doesn’t work with it, it stops with some error. I didn’t want to dig in, so I installed CPython 3.5.3 with pythonz and used that version in the virtual environment. It works again :)

Categories: python Tags:

scraping Steam, get through the age check

Problem
You want to scrape Steam but sometimes Steam brings up an age check. How to get through it from a script? Examples: Fallout: New Vegas (age check), PST: EE (additional maturity check?).

Solution

import requests

COOKIES = {
    'birthtime': '283993201',
    'mature_content': '1',
}
URL = "http://store.steampowered.com/app/2028016/Fallout_New_Vegas_Ultimate_Edition/"

r = requests.get(URL, cookies=COOKIES)

Tip from here.

Categories: python Tags: , ,

Anaconda3, Windows, command-line arguments

April 16, 2017 Leave a comment

Problem
I installed Anaconda3 on Windows 7, but when I wanted to pass a command-line argument to a script, the script didn’t receive the parameter(s). The command-line arguments were simply ignored.

Solution
I found the solution here. This is a blog post from 2010. This issue is still unresolved…

In short: open the registry editor (regedit), find the key HKEY_CLASSES_ROOT\py_auto_file\shell\open\command , and append the string “%*” (without quotes) to the end of the entry. It should look similar to this:

"C:\Anaconda3\python.exe" "%1" %*
Categories: python, windows Tags: , ,

Python Coding Conventions at AIC

March 8, 2017 Leave a comment
Categories: python Tags: , ,

namedtuple

February 9, 2017 Leave a comment

A namedtuple can be used as a simple class where you want to group together some attributes, you want to name them, and you don’t need any methods. As its name suggests, it’s a tuple, but you can assign names to the attribues.

Example

from collections import namedtuple

Point = namedtuple('Point', ['x', 'y'])    # name of the "struct" and its attributes
# Point = namedtuple('Point', 'x y')       # it would also work, and it means the same
                                           # the 2nd parameter can be a single space-delimited string

def main():
    p = Point(x=1, y=4)
    print(p)                # Point(x=1, y=4)
    p = Point(1, 4)
    print(p)                # Point(x=1, y=4)
    print(p.x)              # 1
    print(p[0])             # 1
    print(p == (1, 4))      # True
Categories: python Tags: ,