Line indexing in Python

[Steve Holden]

seafoid wrote:
> Hi Guys,
> 
> When python reads in a file, can lines be referred to via an index?
> 
> Example:
> 
> for line in file:
>      if line[0] == '0':
>          a.write(line)
> 
> This works, however, I am unsure if line[0] refers only to the first line or
> the first character in all lines.
> 
Each time around the loop the variable "line" contains the current line
from the file. Thus line[0] is the first character of the current line.

If your intent is to print all lines beginning with "0" then your code
will work.

> Is there an easy way to refer to a line with the first character being a
> single letter that you know?
> 
You might express it more readably as

for line in file:
    if line.startswith("0"):
        a.write(line)

This seems to express the intent of your code somewhat more directly.

regards
 Steve

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