CODEWITHSUNDEEP
pythonarraysnumpyrounding
IndigoChild
IndigoChild

Reputation: 844

Round() not working

D1_inv
Out[23]: [0.024799999999999999, 0.029600000000000001, 0.035799999999999998]

I'm trying to round these figures upto 4 decimal places. I've used this:

for i in D1_inv:
    round(i,4)

But the output remains the same as above. Can somebody help me here?

Upvotes: 1

Views: 10753

Answers (4)

rahul mehra
rahul mehra

Reputation: 438

D1_inv = [0.024799999999999999, 0.029600000000000001, 0.035799999999999998]

for i in D1_inv:
    print round(float(i), 4)

Output:

0.0248
0.0296
0.0358

Upvotes: 3

Daniel F
Daniel F

Reputation: 14399

What you're seeing is floating-point errors. Often it's not mathematically possible to represent a base 10 decimal in base 2 (i.e. as a float) exactly, so your computer gets as close as it can. But if your output style is set to show many decimal places, these "errors" will show up.

round doesn't help because its output is still a float. You can't really fix this in any simple way, as it is an artefact of binary math. Some options are:

  • Turn the decimals into fractions using frac
  • Fix the diplayed precision of your output using .format (but this makes them strings)
  • fix the displayed precision of your interpeter (which is an interpreter-specific operation).

Upvotes: 3

DYZ
DYZ

Reputation: 57033

Your problem is a perfect case for list comprehension:

D1_inv = [round(i,4) for i in D1_inv]
print(D1_inv)
#[0.0248, 0.0296, 0.0358]

Upvotes: 3

jsmolka
jsmolka

Reputation: 800

You are not saving the result.

for i, x in enumerate(D1_inv):
    D1_inv[i] = round(x, 4)

Upvotes: 0

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