[Biopython] Help for PDBParser

[Nana Trapnest]

Hello,I'd like to know how to print structure of a protein using Biopython, I istalled Python and Biopython, but where I get the proteins? I use this
from Bio.PDB import *parser=PDBParser()structure=parser.get_structure("Tripsina", "2PTC.pdb")print structure
but there is an error...
Traceback (most recent call last):  File "C:/Documents and Settings/Stefania/Desktop/PITON/prova", line 4, in <module>    structure=parser.get_structure("Tripsina", "2PTC.pdb")  File "C:\Python27\lib\site-packages\Bio\PDB\PDBParser.py", line 77, in get_structure    file=open(file)IOError: [Errno 2] No such file or directory: '2PTC.pdb'
Can you help me please???  Where I find 2PTC.pdb??? Thanks