pip install on centos

[root@cent-est utils]# pip install -r requirements.txt
You are using pip version 7.1.0, however version 9.0.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
Collecting pexpect (from -r requirements.txt (line 1))
  Downloading pexpect-4.2.1-py2.py3-none-any.whl (55kB)
    100% |████████████████████████████████| 57kB 1.9MB/s
Collecting pyyaml (from -r requirements.txt (line 2))
  Downloading PyYAML-3.12.tar.gz (253kB)
    100% |████████████████████████████████| 253kB 955kB/s
Collecting ptyprocess>=0.5 (from pexpect->-r requirements.txt (line 1))
  Downloading ptyprocess-0.5.1-py2.py3-none-any.whl
Installing collected packages: ptyprocess, pexpect, pyyaml
  Running setup.py install for pyyaml
Successfully installed pexpect-4.2.1 ptyprocess-0.5.1 pyyaml-3.12
[root@cent-est utils]#