Why doesn't True in Phyton? Help pls!

Question

The following code should be True like in real life. :D

20*1.07==20+20*0.07 #False
20*1.07==20+20*7/100 #False

20+20*0.07==20+20*7/100 #True

Answer 1

here are the results:

20*1.07==20+20*0.7
print(f'{20 * 1.07} == {20 + 20 * 0.7}')
21.400000000000002 == 34.0 -> False

20*1.07==20+20*7/100
print(f'{20 * 1.07} == {20 + 20 *7 / 100}')
21.400000000000002 == 21.4 -> False

20+20*0.7==20+20*7/100
print(f'{20 + 20 * 0.7} == {20 + 20 * 7/ 100}')
34.0 == 21.4 -> False

Answer 2

Avoid comparing floats for equality. You will have rounding and precision problems.
you can use math.isclose() and set your tolerance..

import math

print(24.0001==24)
print(math.isclose(24.0001, 24, abs_tol= 0.1 ))

Answer 3

Szilárd Orbók ,

if precission matters, we can use data type *decimal*. we have to import the modul. this number type has not the issue as floating point numbers.

Answer 4

The representation of floating point numbers is never perfectly accurate. So the equality comparison should not be used.
If you want to allow for the possible tiny rounding error, as Bob_Li suggested use math.isclose() method.
Alternatively you can also use Fraction or decimal types.
https://davidamos.dev/the-right-way-to-compare-floats-in-JUMP_LINK__&&__python__&&__JUMP_LINK/

Answer 5

inputs are always string, you can cast it to int or float depending on your use case.

Answer 6

I just tested the code by assigning the evaluation results for the three expressions and they all are False ...

Now I'm confused ...

Answer 7

Why doesn't True in Phyton? Help pls!

The correct question is:

20*1.07==20+20*0.07 #False
20*1.07==20+20*7/100 #False

20+20*0.07==20+20*7/100 #True

The original problem is 7 percent of something with different solutions.

Answer 8

How to find data type when user enter number

Answer 9

1{20*1.07=21.40000000000002
20+20*0.7=34.0
False}
2{20*1.07=21.4000000000000---2
20+20*7/100=21.4
False}
3{20+20*0.7=21.4000000000-----002
20+20*7/100=21.4
False}

Answer 10

In the first line 0.7 is 0.07. Just a typo. The results are same.