Selenium 使用 Python Geckodriver 可执行文件需要在 PATH 中

我是编程新手，大约两个月前开始学习Python，现在正在复习斯维加特的Automate the Boring Stuff with Python课文.我正在使用IDLE，并且已经安装了Selenium模块和Firefox浏览器.

每当我try 运行webdriver函数时，我都会得到以下结果:

from selenium import webdriver
browser = webdriver.Firefox()

例外情况:

Exception ignored in: <bound method Service.__del__ of <selenium.webdriver.firefox.service.Service object at 0x00000249C0DA1080>>
Traceback (most recent call last):
  File "C:\Python\Python35\lib\site-packages\selenium\webdriver\common\service.py", line 163, in __del__
    self.stop()
  File "C:\Python\Python35\lib\site-packages\selenium\webdriver\common\service.py", line 135, in stop
    if self.process is None:
AttributeError: 'Service' object has no attribute 'process'
Exception ignored in: <bound method Service.__del__ of <selenium.webdriver.firefox.service.Service object at 0x00000249C0E08128>>
Traceback (most recent call last):
  File "C:\Python\Python35\lib\site-packages\selenium\webdriver\common\service.py", line 163, in __del__
    self.stop()
  File "C:\Python\Python35\lib\site-packages\selenium\webdriver\common\service.py", line 135, in stop
    if self.process is None:
AttributeError: 'Service' object has no attribute 'process'
Traceback (most recent call last):
  File "C:\Python\Python35\lib\site-packages\selenium\webdriver\common\service.py", line 64, in start
    stdout=self.log_file, stderr=self.log_file)
  File "C:\Python\Python35\lib\subprocess.py", line 947, in __init__
    restore_signals, start_new_session)
  File "C:\Python\Python35\lib\subprocess.py", line 1224, in _execute_child
    startupinfo)
FileNotFoundError: [WinError 2] The system cannot find the file specified

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<pyshell#11>", line 1, in <module>
    browser = webdriver.Firefox()
  File "C:\Python\Python35\lib\site-packages\selenium\webdriver\firefox\webdriver.py", line 135, in __init__
    self.service.start()
  File "C:\Python\Python35\lib\site-packages\selenium\webdriver\common\service.py", line 71, in start
    os.path.basename(self.path), self.start_error_message)
selenium.common.exceptions.WebDriver例外情况: Message: 'geckodriver' executable needs to be in PATH.

我想我需要将路径设置为geckodriver，但是我不确定如何设置，那么我该如何做呢？