need to get an index for an item in a list

[Roy Smith]

In article <1120418138.615987.160210 at g44g2000cwa.googlegroups.com>,
 nephish at xit.net wrote:

> hey there,
> i need to be able to get the index for an item in a list.
> the list is a list of lines read from a text file.
> 
> like this:
> 
> file = open("/home/somefile.text", "r")
> lines = file.readlines()
> file.close()
> 
> now, i want to see if a certain string is == to one of the lines
> and if so, i need to know the index of that line.

Assuming you're already read the lines from the file with the above code, 
something along the lines of the following will work:

for lineNumber, line in enumerate (lines):
   whatever

But, starting from scratch, it'll be more efficient to do:

for  lineNumber, line in enumerate (file ("filename")):
   whatever

because it'll read lines one at a time as needed, instead of gulping them 
all in at once and buffering them in memory.  For small files (say, less 
than a few hundred lines), it probably won't make any appreciable 
difference, but for big files, it can be substantial.

BTW, enumerate() starts counting from 0; you might want to add 1 to what it 
returns to get a file line number.