On 12/17/2022 3:45 PM, Paul St George wrote:
Thanks to all!
It was the rounding rounding error that I needed to avoid (as Peter J. Holzer
suggested). The use of decimal solved it and just in time. I was about to
truncate the number, get each of the characters from the string mantissa, and
then do something like this:
64550.727
64550 + (7 * 0.1) + (2 * 0.01) + (7 * 0.001)
Now I do not need to!
And that approach would not have helped you, because each of those
calculations would be done as floating point, and you wouldn't have
gotten any more precision (and maybe less) than simply doing
float('64550.727').
Here is a small but interesting discussion thread about float vs Decimal:
https://stackoverflow.com/questions/32053647/comparing-python-decimals-created-from-float-and-string
Would you mind telling us why that degree of precision (that is, decimal
vs float) matters for your problem?
On 17 Dec 2022, at 13:11, Alan Gauld <learn2prog...@gmail.com> wrote:
On 17/12/2022 11:51, Paul St George wrote:
I have a large/long array of numbers in an external file. The numbers look like
this:
-64550.727
-64511.489
-64393.637
-64196.763
-63920.2
When I bring the numbers into my code, they are Strings. To use the
numbers in my code, I want to change the Strings to Float type
because the code will not work with Strings but I do not want
to change the numbers in any other way.
That may be impossible. Float type is not exact and the conversion
will be the closest binary representation of your decimal number.
It will be very close but it may be slightly different when you
print it, for example. (You can usually deal with that by using
string formatting features.)
Another option is to use the decimal numeric type. That has other
compromises associated with it but, if retaining absolute decimal
accuracy is your primary goal, it might suit you better.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
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