Hướng dẫn dùng python rounddown python

You can us either int(), math.trunc(), or math.floor(). They all will do what you want for positive numbers:

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• Inbuilt round() function in Python:
• Understanding the problem with round() method:
• Different ways to round down a number in Python:
• 1) Truncation Method to Round down in Python:
• 2) Using math.floor():
• 3) Using int() to round down a number in python:
• 4) Using numpy.floor() to round down:
• 5) Using // operator to round down in Python:
• Conclusion:
• How do you round down to the nearest 5 in Python?
• How do I reduce decimal places in Python?
• Does Python round .5 up or down?
• How do you round down?

>>> import math
>>> math.floor(12.6)  # returns 12.0 in Python 2
12   
>>> int(12.6)
12
>>> math.trunc(12.6)
12

However, note that they behave differently with negative numbers: int and math.trunc will go to 0, whereas math.floor always floors downwards:

>>> import math
>>> math.floor(-12.6)  # returns -13.0 in Python 2
-13
>>> int(-12.6)
-12
>>> math.trunc(-12.6)
-12

Note that math.floor and math.ceil used to return floats in Python 2.

Also note that int and math.trunc will both (at first glance) appear to do the same thing, though their exact semantics differ. In short: int is for general/type conversion and math.trunc is specifically for numeric types (and will help make your intent more clear).

Use int if you don't really care about the difference, if you want to convert strings, or if you don't want to import a library. Use trunc if you want to be absolutely unambiguous about what you mean or if you want to ensure your code works correctly for non-builtin types.

More info below:

Math.floor() in Python 2 vs Python 3

Note that math.floor (and math.ceil) were changed slightly from Python 2 to Python 3 -- in Python 2, both functions will return a float instead of an int. This was changed in Python 3 so that both methods return an int (more specifically, they call the __float__ method on whatever object they were given). So then, if you're using Python 2, or would like your code to maintain compatibility between the two versions, it would generally be safe to do int(math.floor(...)).

For more information about why this change was made + about the potential pitfalls of doing int(math.floor(...)) in Python 2, see Why do Python's math.ceil() and math.floor() operations return floats instead of integers?

int vs math.trunc()

At first glance, the int() and math.trunc() methods will appear to be identical. The primary differences are:

• int(...)
  • The int function will accept floats, strings, and ints.
  • Running int(param) will call the param.__int__() method in order to perform the conversion (and then will try calling __trunc__ if __int__ is undefined)
  • The __int__ magic method was not always unambiguously defined -- for some period of time, it turned out that the exact semantics and rules of how __int__ should work were largely left up to the implementing class.
  • The int function is meant to be used when you want to convert a general object into an int. It's a type conversion method. For example, you can convert strings to ints by doing int("42") (or do things like change of base: int("AF", 16) -> 175).
• math.trunc(...)
  • The trunc will only accept numeric types (ints, floats, etc)
  • Running math.trunc(param) function will call the param.__trunc__() method in order to perform the conversion
  • The exact behavior and semantics of the __trunc__ magic method was precisely defined in PEP 3141 (and more specifically in the Changes to operations and __magic__ methods section).
  • The math.trunc function is meant to be used when you want to take an existing real number and specifically truncate and remove its decimals to produce an integral type. This means that unlike int, math.trunc is a purely numeric operation.

All that said, it turns out all of Python's built-in types will behave exactly the same whether you use int or trunc. This means that if all you're doing is using regular ints, floats, fractions, and decimals, you're free to use either int or trunc.

However, if you want to be very precise about what exactly your intent is (ie if you want to make it absolutely clear whether you're flooring or truncating), or if you're working with custom numeric types that have different implementations for __int__ and __trunc__, then it would probably be best to use math.trunc.

You can also find more information and debate about this topic on Python's developer mailing list.

Hello coders!! In this article, we will be learning the different ways to round down a number in Python. The rounding of a number is basically making the number simpler while keeping its value close to what it was. Let us see how we can round down a number in Python.

• Inbuilt round() function in Python:
• Understanding the problem with round() method:
• Different ways to round down a number in Python:
• 1) Truncation Method to Round down in Python:
• 2) Using math.floor():
• 3) Using int() to round down a number in python:
• 4) Using numpy.floor() to round down:
• 5) Using // operator to round down in Python:
• Conclusion:

Inbuilt round() function in Python:

In Python, we are provided with a built-in round() function. This function takes two numeric parameters, number and ndigits. It returns the number rounded to ndigits. By default, the value of the ndigits parameter is zero.

Syntax:

round(number, ndigits)

Parameters:

• number – the number which needs to be rounded
• ndigits (optional) – The value up to which the given number needs to be rounded. Its default value is 0.

Return Value:

•  The number n rounded to ndigits.

print(round(12))
print(round(12.7))  
print(round(12.4))

OUTPUT:

12
13
12

We have not passed any value to the ndigits parameter in this example. As a result, it takes the default value, i.e., 0. We can see that the integer number remains at it is, 12.7 is rounded up to 13, and 12.4 is rounded down to 12.

Understanding the problem with round() method:

print(round(2.5))  
print(round(3.5))

OUTPUT:

2
4

As we can see that 2.5 is rounded down to 2, whereas 3.5 is rounded up to 4. Well, this is no glitch in Python programming. It’s just how the round() function works. Let us explore some different ways to round down an integer in Python.

Different ways to round down a number in Python:

We will discuss 5 other methods to round down a number in python except the round() method.

1) Truncation Method to Round down in Python:

As the name suggests, truncation is used to shorten things. It is a straightforward method that can be used to round a number by truncating a given number of digits.

Syntax:

math.trunc(x)

Parameter:

• x -> The decimal number that needs to be truncated.

Return Value:

• Truncated integer part of a number

Example:

import math
print( math.trunc(3.5) )

3

In this example, we have used inbuilt math.trunc() method of Python from the math module to obtain the integer part of the given decimal number.

2) Using math.floor():

A number can be rounded up to a certain digit.

Syntax:

math.floor(x)

Parameter:

• x -> The decimal number that needs to be rounded down.

Return Value:

• The number rounded down to nearest integer.

Example:

import math
print( math.floor(3.5) )

3

As we can see in this example, the number is rounded up to the nearest integer greater than the number itself.

3) Using int() to round down a number in python:

This method is essentially used to convert the given number into integer.

Syntax:

int(value, base)

Paramters:

• value: number or string to be converted to int
• base: number format

Example:

x = 1.3131
x = int(x)
print(x)

1

Here, we used the int() method to convert the decimal number into an integer, thus rounding it down to the nearest possible integer value.

4) Using numpy.floor() to round down:

It is a mathematical function that returns the floor of the elements of array. 

Syntax:

numpy.floor(a)

Parameter:

• a: input array

Return Value:

• array containing the floor value of every element

Example:

import numpy as np
x = np.array([1.22, 1.67, 2.53])
x = np.floor(x)
print(x)

[1. 1. 2.]

As you can see, using the numpy.floor() method, we were able to round down the elements of a given array.

5) Using // operator to round down in Python:

// is the floor division operator of Python.  It returns floor value for both integer and floating-point arguments. 
 

x = 1.3131
x = x // 1
print(x)

Output:

-1

Conclusion:

With this, we come to an end with this article. These are the two ways the number can be rounded down in Python. One can also round down a number using math.ceil() method.

However, if you have any doubts or questions, do let me know in the comment section below. I will try to help you as soon as possible.

Happy Pythoning!

How do you round down to the nearest 5 in Python?

Round a Number Down to the nearest 5 in Python # Call the math. floor() method passing it the number divided by 5 . Multiply the result by 5 . The result of the calculation is the number rounded down to the nearest 5 .

How do I reduce decimal places in Python?

Some of them are discussed below..

Using “%”:- “%” operator is used to format as well as set precision in python. ... .

Using format():- This is yet another way to format the string for setting precision..

Using round(x,n):- This function takes 2 arguments, number, and the number till which we want decimal part rounded..

Does Python round .5 up or down?

As always, Stack Overflow had the answer: Python rounds . 5 down sometimes because of Banker's Rounding, also known by the much more informative name "Round Half To Even". Python will round . 5 numbers to the nearest even whole.

How do you round down?

Rules for Rounding.

If the number you are rounding is followed by 5, 6, 7, 8, or 9, round the number up. Example: 38 rounded to the nearest ten is 40. ... .

If the number you are rounding is followed by 0, 1, 2, 3, or 4, round the number down. Example: 33 rounded to the nearest ten is 30..