CODEWITHSUNDEEP
pythonfloating-pointdecimal
Henrik Hillestad Løvold
Henrik Hillestad Løvold

Reputation: 1291

Printing only significant digits in Python

Given this simple python script:

import sys, math

for i in range(1, len(sys.argv)):
    num = float(sys.argv[i])
    print('sin(%f) = %f' % (num, math.sin(num)))

Run with these arguments:

python hw2a.py 1.4 -0.1 4 99

I want this output:

sin(1.4)=0.98545
sin(-0.1)=-0.0998334
sin(4)=-0.756802
sin(99)=-0.999207

However when I run it, I get a lot of insignificant digits (well, zeroes) behind the decimal point and the significant digits. I know I can specify a fixed number of decimals using for instance %.3f, but how can I make it print all digits behind the decimal point, until there are no significant digits left?

Thanks in advance!

Upvotes: 1

Views: 1672

Answers (2)

Padraic Cunningham
Padraic Cunningham

Reputation: 180441

Use sys.argv[i], no need to convert i to a float and back to a string and g to format:

import sys, math

for i in range(1, len(sys.argv)):
    num = float(sys.argv[i])
    print "sin({}) = {:g}".format(sys.argv[i],math.sin(num))

python foo.py 1.4 -0.1 4 99
sin(1.4) = 0.98545
sin(-0.1) = -0.0998334
sin(4) = -0.756802
sin(99) = -0.999207

If the data is not manually entered as @mhawke suggests, you can use:

print "sin({:g}) = {:g}".format(num, math.sin(num))

Upvotes: 2

tktk
tktk

Reputation: 11734

You can format with %g:

In [16]: a = [1.4, -0.1, 4, 99]

In [18]: for num in a:
    ...:     print('sin(%g) = %g' % (num, math.sin(num)))
    ...:     
sin(-0.1) = -0.0998334
sin(4) = -0.756802
sin(99) = -0.999207

Upvotes: 4

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