DataFrame Python中的数学评估字符串

Question

>>> df['X'].head()
0    25+4
1    25+5
2    15+3
3    20+2
4    20+3
Name: X, dtype: object

How do I evaluate this so my dataframe is this:

>>> df['X'].head()
0    29
1    30
2    18
3    22
4    23

Name: X, dtype: int64

Answer 1

Although there are security concerns, you can use eval to evaluate each element using a lambda expression.

df = pd.DataFrame({'X': ['25+4', '25+5', '15+3', '20+2', '20+3']})

>>> df
      X
0  25+4
1  25+5
2  15+3
3  20+2
4  20+3

>>> df.X.apply(lambda x: eval(x))
0    29
1    30
2    18
3    22
4    23
Name: X, dtype: int64

For a description of security concerns, see:

• Security of Python's eval() on untrusted strings?

• https://nedbatchelder.com/blog/201206/eval_really_is_dangerous.html

• Using python's eval() vs. ast.literal_eval()?