CODEWITHSUNDEEP
pythonlatexsympy
Tim Robinson
Tim Robinson

Reputation: 54764

Aligned LaTeX equations SymPy

SymPy will pretty print expressions within a dict like this:

>>> latex(dict(a=1, b=2))
'\\left \\{ a : 1, \\quad b : 2\\right \\}'

Instead I'd like to use the align environment to split my expressions across lines, with an output like this:

\begin{align}
a & = 1 \\
b & = 2 \\
\end{align}

Can SymPy do this for me?

Upvotes: 4

Views: 585

Answers (1)

user6655984
user6655984

Reputation:

There is no built-in option for this, but you can subclass LatexPrinter and override its method _print_dict to do whatever you want, like this:

from sympy.printing.latex import LatexPrinter

class MyPrinter(LatexPrinter):
    def _print_dict(self, d):
        keys = sorted(d.keys(), key=default_sort_key)
        items = []

        for key in keys:
            val = d[key]
            items.append("%s & = %s" % (self._print(key), self._print(val)))

        return r"\begin{align} %s \end{align}" % r", \\ ".join(items)

Example of use:

mydict = {'a': 1, 'b': 2}
print(MyPrinter().doprint(mydict))   #  \begin{align} a & = 1, \\ b & = 2 \end{align}

The latex function is just a shortcut for LatexPrinter(settings).doprint(expr), you can redefine it accordingly: 

latex = lambda expr, **settings: MyPrinter(settings).doprint(expr)

so that latex has the new behavior.

Speaking of settings, one can also introduce a setting for this, so that both printing methods are available; but at that stage it's probably better to add an issue and PR to SymPy repo.

Upvotes: 1

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