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[Doc] Add slicing and dict-based compositions to Python tutorial

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Ray Speth 2016-04-15 13:00:08 -04:00
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doc/sphinx/cython/tutorial.rst
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@ -126,6 +126,12 @@ fractions (``Y``)::
>>> gas1.X = 'CH4:1, O2:2, N2:7.52'
Mass and mole fractions can also be set using `dict` objects, for cases where
the composition is stored in a variable or being computed::
>>> phi = 0.8
>>> gas1.X = {'CH4':1, 'O2':2/phi, 'N2':2*3.76/phi}
When the composition alone is changed, the temperature and density are held
constant. This means that the pressure and other intensive properties will
change. The composition can also be set in conjunction with the intensive
@ -185,6 +191,27 @@ Or to set the mass fractions while holding temperature and pressure constant::
>>> gas1.TPX = None, None, 'CH4:1.0, O2:0.5'
Working with a Subset of Species
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Many properties of a `Solution` provide values for each species present in the
phase. If you want to get values only for a subset of these species, you can use
Python's "slicing" syntax to select data for just the species of interest. To
get the mole fractions of just the major species in `gas1`, in the order
specified, you can write:
>>> Xmajor = gas1['CH4','O2','CO2','H2O','N2'].X
If you want to use the same set of species repeatedly, you can keep a reference
to the sliced phase object:
>>> major = gas1['CH4','O2','CO2','H2O','N2']
>>> cp_major = major.partial_molar_cp
>>> wdot_major = major.net_production_rates
The slice object and the original object share the same internal state, so
modifications to one will affect the other.
Working With Mechanism Files
----------------------------