全自动区分计算机和人类的公开图灵测试（Completely Automated Public Turing test to tell Computers and Humans Apart）
简称CAPTCHA, 俗称验证码
windows
1.安装tesseract,
安装路径加入path, 设置TESSDATA_PREFIX环境变量
否则报错：
'Error opening data file \exe\Tesseract-OCR\tessdata/eng.traineddata
Please make sure the TESSDATA_PREFIX environment variable is set to the parent directory of your "tessdata" directory.
Failed loading language \'eng\'
Tesseract couldn\'t load any languages!
Could not initialize tesseract.
'
2.pip install pytesseract