How to use bisect.insort_left with a key?

Question

Doc\'s are lacking an example...How do you use bisect.insort_left)_ based on a key?

Trying to insert based on key.

bisect.insort_left(da         


        

Answer 1

Add comparison methods to your class

Sometimes this is the least painful way, especially if you already have a class and just want to sort by a key from it:

#!/usr/bin/env python3

import bisect
import functools

@functools.total_ordering
class MyData:
    def __init__(self, color, number):
        self.color = color
        self.number = number
    def __lt__(self, other):
        return self.number < other.number
    def __str__(self):
        return '{} {}'.format(self.color, self.number)

mydatas = [
    MyData('red', 5),
    MyData('blue', 1),
    MyData('yellow', 8),
    MyData('black', 0),
]
mydatas_sorted = []
for mydata in mydatas:
    bisect.insort(mydatas_sorted, mydata)
for mydata in mydatas_sorted:
    print(mydata)

Output:

black 0
blue 1
red 5
yellow 8

See also: "Enabling" comparison for classes

Tested in Python 3.5.2.

Upstream requests/patches

I get the feeling this is going to happen sooner or later ;-)

• https://github.com/python/cpython/pull/13970
• https://bugs.python.org/issue4356