If I run the following code:
print math.pi, "******", 3.141592653589793
it outputs:
3.14159265359 ****** 3.14159265359
Why is the value being rounded? If I want a more precise value for Pi how would I go about getting it?
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Abe Miessler
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probably it's just `print` that limits the number of decimal places in display. How about `"{0:.15f}".format(pi)`? – The Paramagnetic Croissant Aug 02 '15 at 05:31
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possible duplicate of [How can I format a decimal to always show 2 decimal places?](http://stackoverflow.com/questions/1995615/how-can-i-format-a-decimal-to-always-show-2-decimal-places) – The Paramagnetic Croissant Aug 02 '15 at 05:34
1 Answers
3
>>> print '%d'%math.pi
3
>>> print '%f'%math.pi
3.141593
>>> print '%.10f'%math.pi
3.1415926536
>>> print '%.20f'%math.pi
3.14159265358979311600
>>> print '%.30f'%math.pi
3.141592653589793115997963468544
You could use one of the above to get more digits after the comma printed. When doing calculations, Python use all the digits, but when printing them, Python uses either the default number of digits after comma, or the specified number of digits.
Your hardcoded number may get more digits when printed like this:
>>> print '%.20f'%3.141592653589793
3.14159265358979311600
As you can see the numbers are not 100% equals, the last digits are different. Is if given by the way floating point number are represented in computer memory.
Mihai Hangiu
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You don't happen to know if there is a way to set this globally do you? So that I don't have to do it with every print statement? – Abe Miessler Aug 02 '15 at 05:40
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I do not know. But my intuition says: it is not possible. Personally I always explicitly specify the number of digits after the comma for float numbers, it is safer like this. We should get used with the fact that print displays a representation of the object (i.e. of the float number) and not the object itself. – Mihai Hangiu Aug 02 '15 at 06:17