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PyCon US 2015 videos

April 19, 2015 Leave a comment

PyCon US 2015 took place in Montréal, Canada (just like last year). The videos are being uploaded to pyvideo.org. I think we need some more weeks till all the videos get uploaded but at the moment of writing this post there are already 134 videos available.

Here is a nice script of mine (pyvideo_popularity.py) that orders presentations by popularity.

Categories: python Tags: , ,

Talk Python To Me: a Python podcast

April 10, 2015 Leave a comment

I just found this Python podcast: http://www.talkpythontome.com/. In the latest episode you can find an interview with “Jesse Davis from MongoDB. Jesse is the maintainer for a number of popular open-source projects including the Python MongoDB driver known as PyMongo and Mongo C (for C/C++ developers, yes you read right! C developers). Jesse discusses how interesting it is to write both Python and C code and how it reawakens part of the brain.” (source)

Categories: podcast, python Tags: , ,

UTC now → timestamp → UTC time

January 25, 2015 Leave a comment

Problem
Say you have an application and you want to store the date/time of an event. Later you want to see this date/time.

Solution
Take the current UTC date/time and convert it to a timestamp, which is an integer. Store this value. Then read it and convert it back to UTC date/time.

>>> import datetime
>>>
>>> utcnow = datetime.datetime.utcnow()
>>> utcnow
datetime.datetime(2015, 1, 25, 18, 10, 41, 803198)
>>> ts = int(utcnow.timestamp())
>>> ts
1422205841
>>> datetime.datetime.fromtimestamp(ts)
datetime.datetime(2015, 1, 25, 18, 10, 41)
>>>
Categories: python Tags: , , ,

[mongodb] get a random document from a collection

January 24, 2015 Leave a comment

Problem
From a MongoDB collection, you want to get a random document.

Solution

import random

def get_random_doc():
    # coll refers to your collection
    count = coll.count()
    return coll.find()[random.randrange(count)]

Pymongo documentation on cursors: here.

Categories: python Tags:

opening gzipped JSON files

January 7, 2015 Leave a comment

Problem
I have a project where the input JSON file is almost 7 MB. I keep this project in my Dropbox folder, so that 7 MB text file seems to be a waste. Any way to reduce its size?

Solution
I zipped it up with gzip: “gzip -9 input.json“. This command produced a 1.3 MB “input.json.gz” file and deleted the original. Good. But how to open it in Python?

Normal way (without gzip):

import json

with open("input.json") as f:
    d = json.load(f)

Compressed way (with gzip):

import json
import gzip

with gzip.open("input.json.gz", "rb") as f:
    d = json.loads(f.read().decode("ascii"))

I didn’t notice any performance penalty. The application that first reads this json file starts as fast as before.

Categories: python Tags: ,

pyvenv: create virtual environmets for Python 3.4+

January 1, 2015 Leave a comment

For creating virtual environmets, I’ve used virtualenvwrapper so far. However, Python 3.4 contains the command pyvenv that does the same thing. Since it also installs pip in the virt. env., it can replace virtualenvwrapper.

I like to store my virtual environments in a dedicated folder, separated from the project directory. virtualenvwrapper, by default, stores the virt. env.’s in the ~/.virtualenvs folder. Since I got used to this folder, I will continue to keep my virt. env.’s in this folder.

pyvenv
Say we have our project folder here: ~/python/webapps/flasky_project. Create a virt. env. for this the following way:

pyvenv ~/.virtualenvs/flasky_project

It will create a Python 3 virt. env.

virtualenv / virtualenvwrapper
For the sake of completeness, I also write here how to create virt. env.’s with virtualenv and virtualenvwrapper:

# blog post: http://goo.gl/oEdtT3

# virtualenvwrapper for Python 3 or Python 2
mkvirtualenv -p `which python3` myenv3
mkvirtualenv -p `which python2` myenv2

# virtualenv for Python 3 or Python 2
virtualenv -p python3 myproject3
virtualenv -p python2 myproject2

# When the env. is created, activate it
# and launch the command python within.
# Verify if it's the correct version.

TL; DR
If you use Python 3.4+ and you need a virt. env., use the command “pyvenv“.

2014 in review

December 30, 2014 Leave a comment

The WordPress.com stats helper monkeys prepared a 2014 annual report for this blog.

Here's an excerpt:

The Louvre Museum has 8.5 million visitors per year. This blog was viewed about 190,000 times in 2014. If it were an exhibit at the Louvre Museum, it would take about 8 days for that many people to see it.

Click here to see the complete report.

Categories: python Tags: ,
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