Traceback (most recent call last): File "C:/Users/王丰耳/Desktop/轨道交通票价. py", line 3,in <module> p==3 NameError:name ’p’is not defined >>

This error occurs because the variable "p" has not been defined before it is being used in line 3. The double equal sign (==) is used for comparison, while a single equal sign (=) is used for assignment. To fix this error, you need to define the variable "p" before using it in line 3.