getting file size

[Bob Smith]

Are these the same:

1. f_size = os.path.getsize (file_name)

2. fp1 = file(file_name, 'r')
data = fp1.readlines()
last_byte = fp1.tell()

I always get the same value when doing 1. or 2. Is there a reason I
should do both? When reading to the end of a file, won't tell() be just
as accurate as os.path.getsize ()?

Thanks guys,

Bob

[John Machin]

Re: getting file size


Bob Smith wrote:[color=blue]
> Are these the same:
>
> 1. f_size = os.path.getsize (file_name)
>
> 2. fp1 = file(file_name, 'r')
> data = fp1.readlines()
> last_byte = fp1.tell()
>
> I always get the same value when doing 1. or 2. Is there a reason I
> should do both? When reading to the end of a file, won't tell() be[/color]
just[color=blue]
> as accurate as os.path.getsize ()?
>[/color]

Read the docs. Note the hint that you get what the stdio serves up.
ftell() can only be _guaranteed_ to give you a magic cookie that you
may later use with fseek(magic_coo kie) to return to the same place in a
more reliable manner than with Hansel & Gretel's non-magic
bread-crumbs. On 99.99% of modern filesystems, the cookie obtained by
ftell() when positioned at EOF is in fact the size in bytes. But why
chance it? os.path.getsize does as its name suggests; why not use it,
instead of a method with a side-effect? As for doing _both_, why would
you??