yum update
yum install python3.4 -y
/usr/bin/python* -al
ln -s python3 /usr/bin/python
vi /usr/bin/yum
vi /usr/libexec/urlgrabber-ext-down
python →python2
python -V
python2 -V

yum install python34-setuptools
easy_install-3.4 pip

pip3 install flask

centos更新python3.txt