CODEWITHSUNDEEP
pythonpython-3.x
Shivendra Saxena
Shivendra Saxena

Reputation: 49

Rounding numbers in Python

a=0.005
print ('%.2f'%a)
b=90.005
print('%.2f'%b)
c=90.015
print('%.2f'%c)

Above code is written in python3 and the output is following:

 0.01
 90.00
 90.02

Is this any kind of computational error or m missing a point?

Upvotes: 0

Views: 214

Answers (1)

BcK
BcK

Reputation: 2821

I think the problem here is the second one, which is

b = 90.005
print('%.2f' % b)

Now as @divibisan said, if the digit is between 0-4, it's rounded down, if it's between 5-9, it's rounded up. So why is 90.005 not rounded up ?

Because computers can not represent the floating points precisely. If you look at it closely you will see that 90.005 is represented as,

>>> print('%.50f' % b)
90.00499999999999545252649113535881042480468750000000

That's the reason it is being rounded down, while others behave normally.

>>> print ('%.50f'%a)
0.00500000000000000010408340855860842566471546888351
# 0.01

>>> print ('%.50f'%c)
90.01500000000000056843418860808014869689941406250000
# 90.02

Upvotes: 2

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