Django QuerySet PrettyPrint

pprint_queryset.py

# Enhanced Django QuerySet printing using PrettyPrinter
# Example usage: dropped into and employed within an IPython notebook.

# --- PRETTYPRINT -------------------------------------------------------------
# A PrettyPrinter object contains a _dispatch dictionary.
# This lookup table contains (key, value) pairs wherein the key corresponds to
# an object's __repr__ method, and the value is a special _pprint_<OBJECT>
# method. The PrettyPrint method pprint() queries the dictionary to call the
# appropriate object printer.

# --- _pprint_queryset() ------------------------------------------------------
# This printing method is nearly identical to _pprint_list().
# It is added to the _dispatch dictionary as the QuerySet's __repr__ function.

# --- _pprint_qs() ------------------------------------------------------------
# A wrapper method allowing for easy slicing, stream selection, and simple
# statistical report printing. This method is optional.

# --- Resources ---------------------------------------------------------------
# Derived from: Martjin Pieters: https://stackoverflow.com/a/40828239/4189676
# pprint source: https://github.com/python/cpython/blob/master/Lib/pprint.py
# Indent and modify as you see fit. Please comment with improvements.

import django
import pprint

def _pprint_queryset(printer, object, stream, indent, allowance, context, level) -> None:
    stream.write('<QuerySet [\n ')
    printer._format_items(object, stream, indent, allowance, context, level)
    stream.write('\n]>')

pprint.PrettyPrinter._dispatch[django.db.models.query.QuerySet.__repr__] = _pprint_queryset

def pprint_qs(queryset: django.db.models.query.QuerySet, end: int=10, start: int=0, indent: int=3, stream=None, stats: bool=False) -> None:
    pprint.pprint(queryset[start:end], indent=indent, stream=stream)
    if stats:
        count = queryset.count()
        if count:
            diff = abs(end - start)
            showing = diff if diff < count else count
            coverage = showing / count
            percent_coverage = round(coverage * 100, 3)
            report = f'showing: {showing} of {count} | {percent_coverage}%'
            print('-' * 119)
            print(report.rjust(119))