擅长:python、mysql、java
<pre><code>>>> eqn = Word(alphas,exact=1)+"+"+Word(alphas,exact=1)+"="+Word(alphas,exact=1)
>>> eqn2 = Word(alphas,exact=1)+"="+Word(alphas,exact=1)+"+"+Word(alphas,exact=1
)
>>> equation = eqn|eqn2
>>> equation.parseString("A+b=c")
(['A', '+', 'b', '=', 'c'], {})
>>> equation.parseString("A=b+c")
(['A', '=', 'b', '+', 'c'], {})
>>> equation.parseString("A=b-c")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:\Python26\lib\site-packages\pyparsing.py", line 1032, in parseString
raise exc
pyparsing.ParseException: Expected "+" (at char 3), (line:1, col:4)
</code></pre>