PYTHON > Maths et calculs

OPÉRATIONS

puissance

x**n # x à la puissance n

NOMBRE AU HASARD

randint(a,b) # renvoie un entier entre a et b compris.

 

random() # renvoie un flottant au hasard dans l'intervalle [0 ; 1[

 

uniform(a,b) #renvoie un flottant au hasard entre a et b

0.8129559098175104

12.93990221807783

arrondir un nombre décimal

round(3.1415)
3

round(1.4567,1)
1.5
round(1.4567,2)
1.46

Convertir un nombre réel en entier

int(3.1415)
3

Arrondir une matrice de nombres réels

import numpy as np
a = np.array(([1.24,3.46,5.34]))
a
array([1.24, 3.46, 5.34])
np.around(a, decimals=1)
array([1.2, 3.5, 5.3])

 

>>> import numpy as np
>>> a = np.array(([1,24,3.46,5.34]))
>>> a
array([ 1.  , 24.  ,  3.46,  5.34])
>>> a.astype(int)
array([ 1, 24,  3,  5])

Utiliser format pour incorporer un nombre dans une chaîne de caractères

Si l’objectif est d’arrondir un nombre réel pour ensuite l’insérer dans une chaîne de caractères, le plus simple est d’utiliser format()

'Pi value is {:06.2f}'.format(3.141592653589793)
'Pi value is 003.14'
'Pi value is {:01.2f}'.format(3.141592653589793)
'Pi value is 3.14'

round()

round() takes two numeric parameters, number and ndigits. It returns the number rounded to ndigits. By default, the value of the ndigits parameter is zero.

round(number, ndigits)

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)) -> 12
print(round(12.7)) -> 13
print(round(12.4)) -> 12

Different ways to round down a number in Python:

1) Truncat

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.

Value	Truncated To	Result
12.345	Tens place	10
12.345	Ones place	12
12.345	Tenths place	12.3
12.345	Hundredths place	12.34

math.trunc(x)

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

1 2	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) math.floor()

A number can be rounded up to a certain digit.

Value	Rounded Down To	Result
19.345	Tens place	10
19.345	Ones place	19
19.345	Tenths place	19.3
19.345	Hundredths place	19.34

math.floor(x)

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

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) int()

int(value, base)

value: number or string to be converted to int

base: number format

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) numpy.floor()

numpy.floor(a)

a: input array

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)  // 1

// 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

One can also round down a number using math.ceil() method.

 

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