to_precision
Moved to Bitbucket
https://bitbucket.org/william_rusnack/to-precision/src/master/
Formatting floating point numbers to standard, scientific, or engineering notation with a specified number of significant digits.
Created by:
William Rusnack
GitHub
LinkedIn
Email
Eric Moyer
GitHub
Email
Randle Taylor
GitHub
Use Latest Release
https://github.com/BebeSparkelSparkel/to-precision/releases/tag/0.0.0
Install
pip install git+"link to latest release"
standard notation
to_precision.std_notation(value, precision)
standard notation (US version). http://www.mathsisfun.com/definitions/standard-notation.html
returns a string of value with the proper precision
ex:
>>> std_notation(5, 2)
'5.0'
>>> std_notation(5.36, 2)
'5.4'
>>> std_notation(5360, 2)
'5400'
>>> std_notation(0.05363, 3)
'0.0536'
scientific notation
to_precision.sci_notation(value, precision, delimiter='e'):
scientific notation. https://www.mathsisfun.com/numbers/scientific-notation.html
returns a string of value with the proper precision and 10s exponent delimiter is placed between the decimal value and 10s exponent
ex:
>>> sci_notation(123, 1, 'E')
'1E2'
>>> sci_notation(123, 3, 'E')
'1.23E2'
>>> sci_notation(.126, 2, 'E')
'1.3E-1'
engineering notation
to_precision.eng_notation(value, precision, delimiter='e')
engineering notation. http://www.mathsisfun.com/definitions/engineering-notation.html
returns a string of value with the proper precision and 10s exponent that is divisible by 3 delimiter is placed between the decimal value and 10s exponent
ex:
>>> eng_notation(123, 1, 'E')
'100E0'
>>> eng_notation(1230, 3, 'E')
'1.23E3'
>>> eng_notation(.126, 2, 'E')
'120E-3'
auto notation
to_precision.auto_notation(value, precision, delimiter='e')
Automatically selects between standard notation (US version) and scientific notation. Values in the range 0.001 < abs(value) < 1000 return standard notation.
http://www.mathsisfun.com/definitions/standard-notation.html https://www.mathsisfun.com/numbers/scientific-notation.html
returns a string of value with the proper precision
ex:
>>> auto_notation(123, 4)
'123.4'
>>> std_notation(1234, 4)
'1.234e3'
to_precision
to_precision.to_precision(value, precision, notation='auto', delimiter='e', auto_limit=3, strip_zeros=False, preserve=False)
Converts a value to the specified notation and precision value - any type that can be converted to a float precision - integer that is greater than zero notation - string
- value
- The number to convert
- precision
- The digits of precision
- notation
- 'auto' - selects standard notation when abs(power) < auto_limit else returns scientific notation.
- 'sci' or 'scientific' - returns scientific notation. https://www.mathsisfun.com/numbers/scientific-notation.html
- 'eng' or 'engineering' - returns engineering notation. http://www.mathsisfun.com/definitions/engineering-notation.html
- 'std' or 'standard' - returns standard notation. http://www.mathsisfun.com/definitions/standard-notation.html
- delimiter
- Text that is placed between the decimal value and 10s exponent
- auto_limit
- Integer. When abs(power) exceeds this limit, 'auto' mode will return scientific notation. The default (3) will cause 'auto' mode to return scientific notation for 0.001 < abs(value) < 1000
- strip_zeros
- If true, trailing decimal zeros will be removed.
- preserve_integer
- If true, 'std' will preserve all digits when returning values that have no decimal component.
Implicit vs. Explicit precision
Consider the following data set:
A B C D
---------------- ------------- ------------- -------------
1.00000000000 0.98765432100 0.08700000000 0.00000000234
1.20000000000 1.40000000000 1.00000000000 0.00000000002
1234.00000000000 1.23450000000 0.02345678000 0.00000000000
In a scientific or engineering context, one typically indicates precision explicitly by showing all significant digits. This can be accomplished using to_pecision() with its default arguments.
Using to_precision(x, 3) to render the example data set yields:
A B C D
------ ----- ------ --------
1.00 0.988 0.0870 2.34e-9
1.20 1.40 1.00 2.00e-11
1.23e3 1.23 0.0235 0.00
In a business or informal context one may wish to implicitly specify precision, and render results in their simplest, least cluttered form given that precision. This can be accomplished by invoking the strip_zeros and preserve_integer arguments. Additionally, auto_limit can be used to control the threshold at which scientific notation is adopted.
Using to_precision(x, 3, auto_limit=4, strip_zeros=True, preserve_integer=True) to render the example data set yields:
A B C D
---- ----- ------ -------
1 0.988 0.087 2.34e-9
1.2 1.4 1 2e-11
1234 1.23 0.0235 0
Decimal Notation
to-precision uses decimal notation to indicate precision in cases where the result:
- Is an integer
- Ends with one or more zeros
- All ending zeros are significant
See: https://en.wikipedia.org/wiki/Significant_figures#Significant_figures_rules_explained
For examlple:
>>> to_precision(120, 2)
'120' # Zero is not significant
>>> to_precision(120, 3)
'120.' # Zero is significant
>>> to_precision(100, 2)
'100' # First zero is significant but second is not
>>>
Demonstration
The script demonstration.py demonstrates the behavior of the various options...
$./demonstration.py
Default (Auto Notation):
to_precision(value, precision)
value precision=1 precision=2 precision=3 precision=4 precision=5
------------ ------------- ------------- ------------- ------------- -------------
0 0 0.0 0.00 0.000 0.0000
1 1 1.0 1.00 1.000 1.0000
10 10 10. 10.0 10.00 10.000
...
(many cases)
...
0.000123456 0.0001 0.00012 0.000123 0.0001235 0.00012346
0.001234567 0.001 0.0012 0.00123 0.001235 0.0012346
0.012345678 0.01 0.012 0.0123 0.01235 0.012346
0.123456789 0.1 0.12 0.123 0.1235 0.12346