[英]Evaluate expression in a string in python
I have a string with mathematical operations, how do I evaluate the string within []
to generate the output shown below?我有一个带有数学运算的字符串,如何评估
[]
中的字符串以生成如下所示的 output?
mystring = "[2*3-1] plus [4+2] is equal to [5+6]."
re.findall(r"\[(.*?)\]",mystring) # to find 2*3-1, 4+2, 5+6
Output: "5 plus 6 is equal to 11." # expected output.
You may use re.sub
with eval
and a callback function here:您可以在此处将
re.sub
与eval
和回调 function 一起使用:
mystring = "[2*3-1] plus [4+2] is equal to [5+6]."
output = re.sub(r'\[(.*?)\]', lambda m: str(eval(m.group(1))), mystring)
print(output) # 5 plus 6 is equal to 11.
The strategy here is to match the aritrmetic expression inside every [...]
, which then gets passed to a lambda function.这里的策略是匹配每个
[...]
中的算法表达式,然后将其传递给 lambda function。 There, we call eval()
to get the result, cast to a string and generate the replacement.在那里,我们调用
eval()
来获取结果,转换为字符串并生成替换。
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