+- Python Forum (https://python-forum.io)
+-- Forum: Python Coding (https://python-forum.io/forum-7.html)
+--- Forum: General Coding Help (https://python-forum.io/forum-8.html)
+--- Thread: Why is this multiplication not working? (/thread-1710.html)
Why is this multiplication not working? - klopeks - Jan-21-2017
Hello,I'm very new to Python, and I'm having trouble with some basic math. I've getting a user to input a number and assigning it to a variable. Then I'm multiplying it by the value of another variable, which I've set to 0.1 and displaying the result. When the input is 3, and I multiply it by the other variable, instead of getting .3, I'm getting .3000000000004.
What could cause the multiplication to return what appears to be an incorrect value?
RE: Why is this multiplication not working? - Larz60+ - Jan-22-2017
Show the code, it's impossible to answer correctly without.
RE: Why is this multiplication not working? - klopeks - Jan-22-2017
testMultiplier=0.1
testInput=int(input("Enter a number"))
testOutput=testInput*testMultiplier
print (testOutput)
If I input 3 when asked, it spits out 3.000004
RE: Why is this multiplication not working? - snippsat - Jan-22-2017
Quote:instead of getting .3, I'm getting .3000000000004.It's the way floating point arithmetic work,Basic Answers Python doc.
There is a Decimal module.
>>> 0.4 - 0.1
0.30000000000000004
>>> from decimal import Decimal
>>> Decimal('0.4') - Decimal('0.1')
Decimal('0.3')
RE: Why is this multiplication not working? - klopeks - Jan-22-2017
thanks, that was very helpful.