[Yum] trouble with yum

[airever at wanadoo.fr (russier vincent)]

Hello,
I need help with yum.
I have installed yum-2.2.0 from a rpm package, but it does not wor. I 
get the message :

yum --help
Traceback (most recent call last):
  File "/usr/bin/yum", line 6, in ?
    import yummain
  File "/usr/share/yum-cli/yummain.py", line 23, in ?
    import yum
ImportError: No module named yum

How can I solve the problem ?
Thank you in advance