擅长:python、mysql、java
<pre><code>formula = [
[('VAR', 'x1'), ('PLUS', '+'), ('VAR', 'x2'), ('PLUS', '+'), ('PAR', 'A1')],
[('VAR', 'x1'), ('LESS', '-'), ('VAR', 'x3')],
[('SIN', 'sin'), ('VAR', 'x2'), ('PLUS', '+'), ('PAR', 'A1')]
]
variables = collections.defaultdict(set)
for line_no, line in enumerate(formula):
for typ, value in line:
if typ == 'VAR':
variables[value].add(line_no)
</code></pre>
<blockquote>
<pre><code>variables
</code></pre>
<p>defaultdict(set, {'x1': {0, 1}, 'x2': {0, 2}, 'x3': {1}})</p>
</blockquote>