How to use bisect in Python

The analysis is as follows:

Generally speaking, bisect in Python is used to operate sorted arrays. For example, you can sort while inserting data into an array. The following code demonstrates how to operate:

import bisect
import random
random.seed(1)
print('New pos contents')
print('-----------------')
l=[]
  
for i in range(1,15):
  r=random.randint(1,100)
  position=bisect.bisect(l,r)
  bisect.insort(l,r)
  print '%3d %3d'%(r,position),l

The output result is:

New pos contents
-----------------
 14  0 [14]
 85  1 [14, 85]
 77  1 [14, 77, 85]
 26  1 [14, 26, 77, 85]
 50  2 [14, 26, 50, 77, 85]
 45  2 [14, 26, 45, 50, 77, 85]
 66  4 [14, 26, 45, 50, 66, 77, 85]
 79  6 [14, 26, 45, 50, 66, 77, 79, 85]
 10  0 [10, 14, 26, 45, 50, 66, 77, 79, 85]
 3  0 [3, 10, 14, 26, 45, 50, 66, 77, 79, 85]
 84  9 [3, 10, 14, 26, 45, 50, 66, 77, 79, 84, 85]
 44  4 [3, 10, 14, 26, 44, 45, 50, 66, 77, 79, 84, 85]
 77  9 [3, 10, 14, 26, 44, 45, 50, 66, 77, 77, 79, 84, 85]
 1  0 [1, 3, 10, 14, 26, 44, 45, 50, 66, 77, 77, 79, 84, 85]

You can see that the array is sorted at the same time when inserting these random numbers. However, there are some repeated elements, such as 77,77 above. You can set the order of these repeated elements. If you want the repeated element to appear to the left of the same element, use bisect_left, otherwise use bisect_right, and use insort_left and insort_right accordingly. For example, in the following code, we can see repeated element index changes:

import bisect
import random
random.seed(1)
print('New pos contents')
print('-----------------')
l=[]
  
for i in range(1,15):
  r=random.randint(1,100)
  position=bisect.bisect_left(l,r)
  bisect.insort_left(l,r)
  print '%3d %3d'%(r,position),l

The output result is:

New pos contents
-----------------
 14  0 [14]
 85  1 [14, 85]
 77  1 [14, 77, 85]
 26  1 [14, 26, 77, 85]
 50  2 [14, 26, 50, 77, 85]
 45  2 [14, 26, 45, 50, 77, 85]
 66  4 [14, 26, 45, 50, 66, 77, 85]
 79  6 [14, 26, 45, 50, 66, 77, 79, 85]
 10  0 [10, 14, 26, 45, 50, 66, 77, 79, 85]
 3  0 [3, 10, 14, 26, 45, 50, 66, 77, 79, 85]
 84  9 [3, 10, 14, 26, 45, 50, 66, 77, 79, 84, 85]
 44  4 [3, 10, 14, 26, 44, 45, 50, 66, 77, 79, 84, 85]
 77  8 [3, 10, 14, 26, 44, 45, 50, 66, 77, 77, 79, 84, 85]
 1  0 [1, 3, 10, 14, 26, 44, 45, 50, 66, 77, 77, 79, 84, 85]

This function bisect.bisect(list,key) is like TreeMap in java tailMap(fromkey).

I hope this article will be helpful to everyone’s Python programming.