Enforce better globbing in bar2vtk

[jrwrigh]

Instead of just globbing velbar*.{timestep number}*, have it be more strict by only allowing the * to apply for file extensions.

Example: For time step number = 200: Match:

• velbar.200
• velbar.200.1

Fail:

• velbar.2001
• velbar.20000

[jrwrigh]

The following regex string works for the above cases: ^velbar\.200(?!\d).*$

Effectively, after 200, if the next character is a digit, the matching fails. Otherwise, it succeeds with any other characters.

In [5]: os.listdir('.')      
Out[5]: ['velbar.200', 'velbar.200.1', 'velbar.2000']

In [6]: for filename in filter(re.compile(r'^velbar\.200(?!\d).*$').match, os.listdir('.')):
   ...:     print(filename) 
   ...:                      
velbar.200
velbar.200.1