在 GOOGLE COLAB 中运行此 python 代码时，它向我显示错误。 谁能告诉我我做错了什么并分享更正的代码？

Question

import pandas_datareader.data as web import numpy as np import pandas as pd stock = ['AAPL'] data = web.DataReader(stock,data_source="yahoo",start='01/01/2010')['Adj Close'] data.sort_index(inplace=True) returns = data.pct_change() mean_return = returns.mean() return_stdev = returns.std() annualised_return = round(mean_return * 252,2) annualised_stdev = round(return_stdev * np.sqrt(252),2) print ('The annualised mean return of stock {} is {}, ' 'and the annualised volatility is {}').format(stock[0],annualised_return,annualised_stdev)

Answer 1

You're calling format on the output of the print function by putting it after the close parenthesis. print doesn't return anything, so you're effectively calling None.format(...) (which doesn't exist). You should instead call format on the string directly as such:

print('The annualised mean return of stock {} is {}, and the annualised volatility is {}'.format(stock[0],annualised_return,annualised_stdev))

Answer 2

Here is the corrected code:

import pandas_datareader.data as web

import numpy as np 

import pandas as pd

stock = ['AAPL']

data = web.DataReader(stock,data_source="yahoo",start='01/01/2010')['Adj Close'] 
data.sort_index(inplace=True)

returns = data.pct_change() 

mean_return = returns.mean()

return_stdev = returns.std() 

annualised_return = round(mean_return * 252,2)

annualised_stdev = round(return_stdev * np.sqrt(252),2)

print(f"The annualised mean return of stock {stock[0]} is {annualised_return}, and the annualised volatility is {annualised_stdev}")

So the error came because you did not use af string. An f string puts data in-between the brackets{}

For more info visit: https://www.geeksforgeeks.org/python-output-formatting/#:~:text=In%20Python%2C%20there%20is%20no%20printf%20%28%29%20function,string%20modulo%20%28or%20sometimes%20even%20called%20modulus%29%20operator .

Answer 3

Release notes for pandas_datareader 0.10.0 does mention that there were issues with Yahoo API's requiring headers and were fixed in this release (0.10.0).

Fixed Yahoo readers which now require headers

So, if your google-colab uses any version older than 0.10.0 will have problems using Yahoo API's .

Here are some steps on how to debug the issue in google-colab - jupyter notebook .
Step 1: Determine the installed version of module pandas_datareader .

!pip show pandas_datareader

Step 2: if the version is lower than 0.10.0 then upgrade the version.

!pip install --upgrade pandas_datareader

Step 3: Don't forget to restart the runtime to load the new libraries.

Press Runtime->Restart runtime

Step 4: Now try running the step 1 again to determine if the newest version is installed.

!pip show pandas_datareader

I hope the newest version will be installed and you can run your above code with the correction mentioned by @ Aaron in his answer.

Note: ! is required before shell commands. Try going thorugh the official docs of IPython for more info.