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pythonprecisionvalueerror
Ryan pietras
Ryan pietras

Reputation: 39

trouble with using variables as format precision

I have been trying to use a variable as a specifer in float precision to try to limit the number of decimal places shown for pi:

num = float(input("What decimal point do you want pi to be displayed to?(Up to 15) "))

print(format(math.pi, '.(num)f'))

when i run it, it shows the ValueError: Format specifier missing precision

I was wondering if there was any other way of writing it so i would be able to use a variable. Im pretty new and its probably a really simple mistake, but i dont know.

Thanks for any help :D

Upvotes: 3

Views: 974

Answers (2)

Joran Beasley
Joran Beasley

Reputation: 114038

you can just pass it in as a format argument ...

num="3"
print("{pi:0.{num}f}".format(pi=22/7.0,num=num))

Upvotes: 2

blhsing
blhsing

Reputation: 106891

You can use the string formatting operator with .* as the formatting option:

from math import pi
print('%.*f' % (5, pi))

This outputs:

3.14159

Upvotes: 1

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