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Diffstat (limited to 'docs/tutorial.rst')
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1 files changed, 32 insertions, 2 deletions
diff --git a/docs/tutorial.rst b/docs/tutorial.rst index b11e608..2894c0b 100644 --- a/docs/tutorial.rst +++ b/docs/tutorial.rst @@ -89,7 +89,7 @@ If you ask Pint to perform an invalid conversion: >>> speed.to(ureg.joule) Traceback (most recent call last): ... - pint.errors.DimensionalityError: Cannot convert from 'inch / minute' ([length] / [time]) to 'joule' ([length] ** 2 * [mass] / [time] ** 2) + DimensionalityError: Cannot convert from 'inch / minute' ([length] / [time]) to 'joule' ([length] ** 2 * [mass] / [time] ** 2) Sometimes, the magnitude of the quantity will be very large or very small. The method 'to_compact' can adjust the units to make the quantity more @@ -170,7 +170,7 @@ If you try to use a unit which is not in the registry: >>> speed = 23 * ureg.snail_speed Traceback (most recent call last): ... - pint.errors.UndefinedUnitError: 'snail_speed' is not defined in the unit registry + UndefinedUnitError: 'snail_speed' is not defined in the unit registry You can add your own units to the registry or build your own list. More info on that :ref:`defining` @@ -303,6 +303,22 @@ Pint supports float formatting for numpy arrays as well: >>> # scientific form formatting with unit pretty printing >>> print('The array is {:+.2E~P}'.format(accel)) The array is [-1.10E+00 +1.00E-06 +1.25E+00 +1.30E+00] m/s² + +Pint also supports 'f-strings'_ from python>=3.6 : + +.. doctest:: + + >>> accel = 1.3 * ureg['meter/second**2'] + >>> print(f'The str is {accel}') + The str is 1.3 meter / second ** 2 + >>> print(f'The str is {accel:.3e}') + The str is 1.300e+00 meter / second ** 2 + >>> print(f'The str is {accel:~}') + The str is 1.3 m / s ** 2 + >>> print(f'The str is {accel:~.3e}') + The str is 1.300e+00 m / s ** 2 + >>> print(f'The str is {accel:~H}') + The str is 1.3 m/s² But Pint also extends the standard formatting capabilities for unicode and LaTeX representations: @@ -336,6 +352,18 @@ If you want to use abbreviated unit names, prefix the specification with `~`: The same is true for latex (`L`) and HTML (`H`) specs. +.. note:: + The abbreviated unit is drawn from the unit registry where the 3rd item in the + equivalence chain (ie 1 = 2 = **3**) will be returned when the prefix '~' is + used. The 1st item in the chain is the canonical name of the unit. + +The formatting specs (ie 'L', 'H', 'P') can be used with Python string 'formatting +syntax'_ for custom float representations. For example, scientific notation: + +..doctest:: + >>> 'Scientific notation: {:.3e~L}'.format(accel) + 'Scientific notation: 1.300\\times 10^{0}\\ \\frac{\\mathrm{m}}{\\mathrm{s}^{2}}' + Pint also supports the LaTeX siunitx package: .. doctest:: @@ -409,3 +437,5 @@ also define the registry as the application registry:: .. _eval: http://docs.python.org/3/library/functions.html#eval .. _`serious security problems`: http://nedbatchelder.com/blog/201206/eval_really_is_dangerous.html .. _`Babel`: http://babel.pocoo.org/ +.. _'formatting syntax': https://docs.python.org/3/library/string.html#format-specification-mini-language +.. _'f-strings': https://www.python.org/dev/peps/pep-0498/
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