无法替换Jupyter Notebook数据框中的字符串符号“-”

Question

I import data from "url = (" http://finviz.com/quote.ashx?t= " + symbol.lower())"

and got the table:

        P/B    P/E Forward P/E   PEG Debt/Eq EPS (ttm) Dividend %     ROE  \
AMZN  18.73  92.45       56.23  2.09    1.21     16.25          -  26.70%   
GOOG   4.24  38.86           -  2.55       -     26.65          -       -   
PG     4.47  22.67       19.47  3.45    0.61      4.05      3.12%  18.80%   
KO    11.04  30.26       21.36  4.50    2.45      1.57      3.29%  15.10%   
IBM    5.24   9.28        8.17  9.67    2.37     12.25      5.52%  30.90%   

         ROI   EPS Q/Q Insider Own  
AMZN   3.50%  1026.20%      16.20%  
GOOG       -    36.50%       5.74%  
PG    13.10%    15.50%       0.10%  
KO    12.50%    56.80%       0.10%  
IBM   17.40%     0.70%       0.10%  

Then I was trying to convert string to float:

df = df[(df['P/E'].astype(float)<20) & (df['P/B'].astype(float) < 3)] 

and got "ValueError: could not convert string to float:"

I think that values 0.70% and sign "-" is the problem.

I tried:

df.replace("-","0")
df.replace('-', 0)
df.replace('-', nan)

But nothing works.

Answer 1

You may need to assign it back

df=df.replace("-","0")

And I recommend to_numeric

df['P/E']=pd.to_numeric(df['P/E'],errors = 'coerce')
df['P/B']=pd.to_numeric(df['P/B'],errors = 'coerce')

Answer 2

You should use numpy:

import numpy as np

then the next replacement:

df = df.replace('-', np.nan)

Next, change the datatype:

df = df['Forward P/E'].astype(float)

Lastly, you can test if the datatype is float64.