Generating and Returning PDF as response in Django

We might need to generate a receipt or a report in PDF format in Django app. In this article, we will see how to generate a dynamic PDF from html content and return it as a response.

Create a Django project. If you are not using virtual environment, we strongly recommend to do so.

Installing Dependencies:

Once virtual environment is ready and activated, install the below dependencies.

For pdfkit  to work, we need wkhtmltopdf  installed in our Linux system.

Continue reading “Generating and Returning PDF as response in Django”

Using signals in Django to log changes in models

Sometimes we need to know who made what changes to which table. This might be required for legal audit purpose or for simple organisational level logging.

There are multiple Django apps available online which can help you log the model changes but there is no fun in doing that. We will see how to do it without using ready-made app and hence will learn something in the process.

Signals:

Signals lets a sender notify another receiver that some event have occurred and some action needs to be performed.

For example, we have some data in cache as well in DB. We read data from cache and if not found then goes to DB as fallback. Now whenever a DB is updated, we need to update the cache as well. But we might update the model from multiple views. Hence it is tough and not clean to write cache update logic in every such view. Signals comes into picture now.

Continue reading “Using signals in Django to log changes in models”

py_instagram_dl – The Python Package to Download All pictures of an Instagram User

I created a small script to download all pictures of an Instagram user without using APIs as APIs poses few limitations like rate limit.

After few rounds of tweaking, optimisation and beautifying code, I though of creating a python package out of it. If you want to know how to create a distributable python package, this article will be extremely helpful as steps are discussed in great detail.

You can find the  py_instagram_dl  package listed on pypi.
link is –  https://pypi.python.org/pypi/py-instagram-dl.

How to download all pictures of an Instagram user:
  • Create a virtual environment. Optional but strongly recommended. You may follow this simple and step by step pocket guide on Python Virtual Environment.
  • Install dependencies. This package instead few other python packages to work.
  • Now install this package.
  • Use the installed package in your code.
    Parameter Options:
Download  method have one mandatory and two optional parameters as of now.

Mandatory Parameter:
Parameter 1: Valid username of Instagram user.

Optional Parameter:
verbose
: default value – True (boolean) : Decides whether information should be printed on screen. Recommended to have it set to True so that in case of large number of downloads you can make sure script is working and is not just freezed.

wait_between_requests : default value – 0 (integer) : This is the time in seconds for which scripts waits to send new hit to download the picture to Instagram. It is recommended to pass a positive value for this parameter. If you are getting rate limit exceptions after downloading few pictures, pass 1 in this parameter, i.e. wait for 1 second between each request.

Exceptions:

InvalidUsernameException: When a non existent username is provided.
RateLimitException: When rate limit is reached. Use parameter wait_between_requests  to avoid this.

 

Source code.

Virtual Environment in Python – A Pocket Guide

In almost every article, we recommended the use of virtual environment for developing any Python or Django project.

In this article, we will briefly cover the virtual environment in python, installation and usage.

What is a Virtual Environment:

Virtual environment is an isolated python environment which can be created using virtualenv python tool. This virtual environment contains all the packages that a python package would require. Python project running in virtual environment does not use the system wide installed python package.

Continue reading “Virtual Environment in Python – A Pocket Guide”