Syntax and Description
__ceil__() method implements the behavior of the
math.ceil() function. For example, if you attempt to call
math.ceil(x), Python will run the
x.__ceil__() method to obtain the return value.
We call this a “Dunder Method” for “Double Underscore Method” (also called “magic method”). To get a list of all dunder methods with explanation, check out our dunder cheat sheet article on this blog.
The following code snippet overrides the
__ceil__() dunder method to return the “rounded up” age of a
Person when you pass an object of type
Person into the
import math class Person: def __init__(self, age): self.age = age def __ceil__(self): floor_value = int(self.age) if floor_value < self.age: return floor_value + 1 return floor_value alice = Person(42.42424242) print(math.ceil(alice)) # 43 bob = Person(42.0) print(math.ceil(bob)) # 42
How to fix “TypeError: must be real number, not XXX”?
Note that without defining the
__ceil__() method, Python would’ve raised a
import math class Person: def __init__(self, age): self.age = age alice = Person(42.42424242) print(math.ceil(alice))
Traceback (most recent call last): File "C:\Users\...\code.py", line 12, in <module> print(math.ceil(alice)) TypeError: must be real number, not Person
To fix this
TypeError, simply define the
__ceil__() method as outlined in the first code snippet in this article.
Next we will look at the ceil function
⌈⋅⌉. Just as the floor function is the real number
x rounded down,
⌈x⌉ is just
x “rounded up”, i.e. the smallest integer greater than
For instance, if
x=9.1, then the ceil of
x is just
10. On the other hand, if
x=−9.1, then the smallest integer greater than
x is an integer, then its ceil is just itself.
If we phrase this in terms of the integer and fractional part from before, we get
You can see from the above discussion that if
x is not an integer, then
You can read more in our full guide:
Where to Go From Here?
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