Archive for the ‘python’ Category

[ C lang] reading a text file line by line

February 22, 2020 Leave a comment

I had a text file that I was reading line by line in C. Every line was tokenized. The file looked like this:

1978	Aachen Cathedral	DE	C	EUR	0	3
1978	City of Quito	EC	C	LAC	70	2
1978	Galápagos Islands	EC	N	LAC	14066514	1

I converted every year to an integer. From the 2nd line I got 1978 (as int), but in the first line the string to int conversion failed.

It turned out that the token “1978” in the first line was 7 characters long, not 4. At that point I opened the file in a hex editor and there were 3 special bytes at the beginning: EF BB BF. This is a byte order mark (BOM).


As a quick fix, I removed those 3 bytes in the hex editor.

I tried it under Python too and it caused a problem there too:

>>> f = open("input.txt")
>>> s = f.readline()
>>> s
'\ufeff1978\tAachen Cathedral\tDE\tC\tEUR\t0\t3\n'
>>> s.split()
['\ufeff1978', 'Aachen', 'Cathedral', 'DE', 'C', 'EUR', '0', '3']
>>> s.split()[0]
>>> int(s.split()[0])
Traceback (most recent call last):
  File "", line 1, in
ValueError: invalid literal for int() with base 10: '\ufeff1978'

If you know how to ignore those bytes during file read, please leave a comment. I’m interested in both C and Python solutions.

crop images easily

November 2, 2019 Leave a comment

You have lots of images and you want to crop them. How to do it without losing your hair?

I just found a nice little hobby project for this:

Under Manjaro, I had to install tkinter too: “sudo pacman -S tk“.

Reddit discussion here.

Categories: python Tags: , ,

QuickJump: bookmark your directories and switch between them easily

June 30, 2019 Leave a comment

I made a little project that facilitates jumping between directories in the command line. You can find it here: . Visit the GitHub page for more info.


Categories: python, shell Tags: , , , ,

Getting started on Twitter

January 2, 2018 Leave a comment

You have a site and you want to create a Twitter site for it too where you want to send posts, probably in an automatic way.

If you have a gmail account, you can use it to create several Twitter accounts. The trick is to make the e-mail addresses different with a dot. Example: and . If you send an e-mail to these addresses, they’ll arrive in the same mailbox, though Twitter treats them as two different addresses.

Then, follow the steps at to register your app.

Sample Python code
Here is a simple example to post a tweet:

#!/usr/bin/env python3

import config as cfg
import tweepy

def get_api(cfg):
    d = cfg.twitter_keys
    auth = tweepy.OAuthHandler(d['consumer_key'], d['consumer_secret'])
    auth.set_access_token(d['access_token'], d['access_token_secret'])
    return tweepy.API(auth)

def main():
    api = get_api(cfg)
    tweet = "just a test"
    status = api.update_status(status=tweet)    # update_status -> send a tweet

if __name__ == "__main__":
Categories: python, web Tags: , , , ,

TLDR: simplified and community-driven man pages

November 24, 2017 Leave a comment

The TLDR pages are a community effort to simplify the beloved man pages with practical examples.


(I also have a similar project called PrimCom but it has never become popular.)

Categories: bash, python Tags: ,

[android] Mobile C

September 18, 2017 Leave a comment

If you want to develop a C or Python program on your Android device, try Mobile C. Write your program, press a button, and it’s compiled (or interpreted) and executed. Several languages are supported: C, C++ 11, Python 3, JavaScript, Lua.

Categories: android, python Tags:

web server on localhost

September 14, 2017 2 comments

I wanted to share a 3.3 GB big zip file with my students.

I love Python, so I chose this simple trick: “python3 -m http.server“. It starts a web server and makes the content of the current directory available. I shared the URL with my students (10 people) and they started to download the big file at the same time. And it turned out that Python was not a good choice here since only 1 person could download the file and the others had to wait. This solution is single-threaded :(

I hate Node.js but this time it provided the winning solution. Node.js’s async nature was perfect for the job, it could serve several clients. The download rate was not super fast, but at least it worked (and it worked well).

The following tip is from here.

$ sudo npm install http-server -g
[sudo] password for jabba: 
/trash/opt/node-v5.1.0-linux-x64/bin/http-server -> /trash/opt/node-v5.1.0-linux-x64/lib/node_modules/http-server/bin/http-server
/trash/opt/node-v5.1.0-linux-x64/bin/hs -> /trash/opt/node-v5.1.0-linux-x64/lib/node_modules/http-server/bin/http-server

I couldn’t launch it with “http-server“, but the full path “/trash/opt/node-v5.1.0-linux-x64/lib/node_modules/http-server/bin/http-server” did the trick.

Update (20171123)
Following the instructions at, I upgraded my Node.js to version 6.12.0. Then, installing http-server (with sudo npm install http-server -g), I got a link at “/usr/bin/http-server” that pointed to “/usr/lib/node_modules/http-server/bin/http-server“. Thus, I could start “http-server” without modifying the PATH.

Categories: python Tags: , ,