python requirements.txt 里指定操作系统和python版本

参考https://pip.pypa.io/en/stable/reference/requirement-specifiers/

# --------------------------------- # System platform value # --------------------------------- # AIX "aix" # Linux "linux" # Windows "win32" # Windows/Cygwin "cygwin" # MacOS "darwin" # --------------------------------- atomac==1.1.0; sys_platform == 'darwin' futures>=3.0.5; python_version < '3.0' futures>=3.0.5; python_version == '2.6' or python_version=='2.7'