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pythonfile-iofloating-pointprecision
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Reputation: 5642

Python Output to File Higher Floating Point Precision

The following:

>>>import struct
>>>struct.unpack('!d', ('40d11998e5035288').decode('hex'))[0]
>>>
>>>17510.3889778429

I would like to be able to print the value 17510.3889778429 to a .csv output file. For some reason, when I write this to a file, it rounds the decimal and only writes:

17510.3889778

How would I print this with higher precision?

Thanks, Ned

Upvotes: 2

Views: 4995

Answers (2)

Russell Borogove
Russell Borogove

Reputation: 19037

Assuming you're using Python's csv module, the documentation says that non-string data is formatted using str(), and that seems to be where the truncation is happening. So one thing you could do is define your own class that stringizes the way you want:

class myFloat( float ):
    def __str__(self):
        return "%.12f"%self

 x = myFloat( 17510.3889778429 )
 print "%s"%x

Yields:

17510.388977842900

Upvotes: 3

Mark Ransom
Mark Ransom

Reputation: 308276

You can convert the number to a string using any appropriate method and write the string to the CSV.

>>> x = 17510.3889778429
>>> s = str(x)
>>> s
'17510.3889778'
>>> s = '%17.11f' % x
>>> s
'17510.38897784290'

Upvotes: 1

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