Use Python bisect module

Use Python bisect module

A, bisect module brief introduction:

Python的bisect模块是内置模块，用于维护有序列表，它采用二分法来排序插入

bisect What are some ways:

# 首先导入bisect包
import bisect
print(dir(bisect))
# 输出结果：
['__builtins__', '__cached__', '__doc__', '__file__',
 '__loader__', '__name__', '__package__', '__spec__',
 'bisect', 'bisect_left', 'bisect_right', 'insort',
 'insort_left', 'insort_right']

Above these methods, in addition to magic methods, others explain in detail:

bisect : Returns the index element is inserted in the list

my_list = [1, 3, 5, 7, 9]
result = bisect.bisect(my_list, 6)
print(result)

# 输出结果：3 表示插入元素在列表中的下标

bisect_left : default element will be found to the left, to the left of return insert subscript

my_list = [1, 3, 5, 7, 9]
result = bisect.bisect_left(my_list, 6)
print(result)

# 输出结果： 3 同bisect方法

bisect_right : In contrast with bisect_left

my_list = [1, 5, 3, 9, 7]
result = bisect.bisect_right(my_list, 6)
print(result)

# 输出结果： 3 

insort : inserts element in the list to the correct location

# 若列表中的元素是有序的话
my_list = [1, 3, 5, 7, 9]
bisect.insort(my_list, 2)
print(my_list)

# 输出结果：[1, 2, 3, 5, 7, 9]

# 若列表中的元素是无序的话，默认插入到最右边
my_list = [2, 3, 1, 5, 7, 4]
bisect.insort(my_list, 6)
print(my_list)

# 输出结果：[2, 3, 1, 5, 7, 4, 6]

insort_left : left interpolation value, the return value None

my_list = [1, 3, 5, 7, 9]
bisect.insort_left(my_list, 2)
print(my_list)

# 输出结果：[1, 2, 3, 5, 7, 9]

insort_right : To insert a value returns None

my_list = [1, 3, 5, 7, 9]
bisect.insort_right(my_list, 6)
print(my_list)

# 输出结果：[1, 3, 5, 6, 7, 9]

insort_left and insort_right: just insert location is different

Second, the use scenarios:

For chestnut to grading, student achievement (0-100) based on student achievement, classified into (ABCDEF):

General operation:

def grade(score):
    if score < 60:
        return 'F'
    elif score < 70:
        return 'E'
    elif score < 80:
        return 'D'
    elif score < 90:
        return 'C'
    elif score < 100:
        return 'B'
    else:
        return 'A'


scores = [59, 60, 72, 82, 85, 90, 98, 100]
result = [grade(item) for item in scores]
print(result)

# 输出结果如下:
['F', 'E', 'D', 'C', 'C', 'B', 'B', 'A']

Operation bisect use of:

• For example, student achievement classification cut-off point is [60, 70, 80, 90, 100], grades are'FEDCBA'

  def grade(score, points=[60, 70, 80, 90, 100], grade="FEDCBA"):
      item = bisect.bisect(points, score)
      return grade[item]
  
  
  scores = [101, 60, 72, 82, 85, 90, 98, 100]
  result = [grade(item) for item in scores]
  print(result)
  
  # 输出结果如下：
  ['A', 'E', 'D', 'C', 'C', 'B', 'B', 'A']
  

• Mall membership points to grade:

  def grade(score, points=[60, 70, 80, 90, 100], grade="FEDCBA"):
      item = bisect.bisect(points, score)
      print(grade[item])
      return grade[item]
  
  
  scores = [1000, 2000, 3000]
  names = ['普通会员', '中级会员', '高级会员', 'VIP']
  values = [999, 1999, 2999, 3001]
  print([grade(item, points=scores, grade=names) for item in values])
  
  # 输出结果如下：['普通会员', '中级会员', '高级会员', 'VIP']