I want to do a single regression analysis with python.

I'd like to do a single regression analysis on python's jupyter notebook, but one of the data is saved as df1, but the csv on the other x axis is not saved, so I'd like to do a single regression analysis as [1,2,3,........], but I don't know how to do it.

from sklearn.linear_model import LinearRegression

lr = LinearRegression()
lr.fit(x,y1)

Name Error Traceback (most recent call last)
<ipython-input-91-bc6b4eab4f87>in<module>
     2
     3 lr = LinearRegression()
---->4 lr.fit(x,y1)

NameError: name 'x' is not defined

I don't know how to make the part that corresponds to x.