Problems with float and "6" type

Hi, I am having problems both in the Windows version on the Linux
version of Python as put some number with some 6 type that it always
returns a value me, following examples:

>>> 2.0
2.0
>>> 1.55
1.55
>>> 1.56
1.5600000000000001
>>> 1.6
1.6000000000000001
>>> 1.63
1.6299999999999999
>>> 1.64
1.6399999999999999
>>> 1.71
1.71
>>> 6.0
6.0

Recalling that the error happens only with the digit 6 in float.
Thanks for attention.

Pedro Clemente Pereira Neto 
Brasil
pedrocpneto at gmail.com