python html如何转成PDF?

import pdfkit
pdfkit.from_url('http://www.cocoachina.com/', 'out.pdf')

• 老报错我已经安装了wkhtmltopdf :还请大神帮忙解决!

• 还有如何将wkhtmltopdf的执行路径添加到系统环境$PATH变量中?

Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pdfkit/configuration.py", line 21, in __init__
    with open(self.wkhtmltopdf) as f:
FileNotFoundError: [Errno 2] No such file or directory: b''

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/peibobo/PycharmProjects/bottle/pdf_test.py", line 3, in 
    pdfkit.from_url('http://www.cocoachina.com/', 'out.pdf')
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pdfkit/api.py", line 24, in from_url
    configuration=configuration, cover_first=cover_first)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pdfkit/pdfkit.py", line 42, in __init__
    self.configuration = (Configuration() if configuration is None
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pdfkit/configuration.py", line 27, in __init__
    'https://github.com/JazzCore/python-pdfkit/wiki/Installing-wkhtmltopdf' % self.wkhtmltopdf)
OSError: No wkhtmltopdf executable found: "b''"
If this file exists please check that this process can read it. Otherwise please install wkhtmltopdf - https://github.com/JazzCore/python-pdfkit/wiki/Installing-wkhtmltopdf