[Tutor] open file form

[Cliff Martin]

Hi,

A few days ago I asked for some help with an ASCII file. It was a large 
file which I needed to read all the data into a file. (It's an 
interferometry file so I can't manipulate it line by line, especially if 
I want to fit it to orthogonal poynomials).  I got help back (thanks 
dman and Rick Pasotto) but in one case someone used a form for opening a 
file like:

f = 3D file(filename)

then manipulated the opened file using 3D. etc.  When I tried this it 
didn't work.  Then today on a completely different question I saw the 
same form again.  What is this form? I can't seem to find it in the 
doc's and the following is what I get when I try it.  Thanks in advance 
for the help.

f =3D file('c:/transfer/doctst.txt')
Traceback (  File "<interactive input>", line 1
    f =3D file('c:/transfer/doctst.txt')
        ^
SyntaxError: invalid syntax

Cliff