skip last line in loops

[eight02645999]

hi,
how can i skip printing the last line using loops (for /while)

eg

for line in open("file):
print line.

I want to skip printing last line of the file.thanks

[James Stroud]

ei***********@yahoo.com wrote:

hi,
how can i skip printing the last line using loops (for /while)

eg

for line in open("file):
print line.

I want to skip printing last line of the file.thanks

afile = open(filename)

xlines = afile.xreadlines()

aline = xlines.next
for nextline in xlines:
print aline
aline = nextline

James

[James Stroud]

James Stroud wrote:

ei***********@yahoo.com wrote:

>hi,
how can i skip printing the last line using loops (for /while)

eg

for line in open("file):
print line.

I want to skip printing last line of the file.thanks

afile = open(filename)

xlines = afile.xreadlines()

aline = xlines.next
for nextline in xlines:
print aline
aline = nextline

James

Shoule be

aline = xlines.next()

[tac-tics]

Try:
afile = open(filename)
lines = afile.readlines()[:-1] # assigns all except the last element to
a list "lines"
for line in lines:
print line

[Fredrik Lundh]

ei***********@yahoo.com wrote:

how can i skip printing the last line using loops (for /while)

eg

for line in open("file):
print line.

I want to skip printing last line of the file.

do it lazily:

last_line = None
for line in open("file):
if last_line:
print last_line
last_line = line

or just gobble up the entire file, and slice off the last item:

for line in list(open("file"))[:-1]:
print line

</F>

[eight02645999]

Fredrik Lundh wrote:

ei***********@yahoo.com wrote:

how can i skip printing the last line using loops (for /while)

eg

for line in open("file):
print line.

I want to skip printing last line of the file.

do it lazily:

last_line = None
for line in open("file):
if last_line:
print last_line
last_line = line

or just gobble up the entire file, and slice off the last item:

for line in list(open("file"))[:-1]:
print line

</F>

hi
would it be a problem with these methods if the file is like 20Gb in
size...?

[Roberto Bonvallet]

ei***********@yahoo.com wrote:

>do it lazily:

last_line = None
for line in open("file):
if last_line:
print last_line
last_line = line

or just gobble up the entire file, and slice off the last item:

for line in list(open("file"))[:-1]:
print line

</F>

hi
would it be a problem with these methods if the file is like 20Gb in
size...?

The second one would be a problem, since it creates a list containing all
the lines of the file. Use the lazy approach.

--
Roberto Bonvallet

[James Stroud]

ei***********@yahoo.com wrote:

Fredrik Lundh wrote:

>ei***********@yahoo.com wrote:

>>how can i skip printing the last line using loops (for /while)

eg

for line in open("file):
print line.

I want to skip printing last line of the file.

do it lazily:

last_line = None
for line in open("file):
if last_line:
print last_line
last_line = line

or just gobble up the entire file, and slice off the last item:

for line in list(open("file"))[:-1]:
print line

</F>

hi
would it be a problem with these methods if the file is like 20Gb in
size...?

See the documentation for xreadlines.

James

[Fredrik Lundh]

James Stroud wrote:

See the documentation for xreadlines.

why?

</F>

[Paul Rubin]

ei***********@yahoo.com writes:

for line in open("file):
print line.

I want to skip printing last line of the file.thanks

def all_but_last(it): # yield all but last item of an iterator
a = it.next()
for b in it:
yield a
a = b

for line in all_but_last(open("file")):
print line

[Daniel Klein]

On 14 Dec 2006 22:47:23 -0800, ei***********@yahoo.com wrote:

>hi,
how can i skip printing the last line using loops (for /while)

eg

for line in open("file):
print line.

I want to skip printing last line of the file.thanks

while True:
line1 = myfile.readline()
if not line1: break
line2 = myfile.readline()
if line2:
print line1
else:
break
Dan

[Fredrik Lundh]

ei***********@yahoo.com wrote:

>do it lazily:

last_line = None
for line in open("file):
if last_line:
print last_line
last_line = line

or just gobble up the entire file, and slice off the last item:

for line in list(open("file"))[:-1]:
print line

</F>

would it be a problem with these methods if the file is like 20Gb in
size...?

not with the lazy version, of course. the "gobble up" version will
load the entire file into memory.

but cutting off a single line from a 20 gigabyte file by looping over
it sounds like a bit contrived, really. if you're really doing this
(why?), maybe you should just truncate the file in place instead.

</F>

[James Stroud]

Fredrik Lundh wrote:

James Stroud wrote:

>See the documentation for xreadlines.

why?

</F>

5.16 xreadlines -- Efficient iteration over a file

[Peter Otten]

James Stroud wrote:

Fredrik Lundh wrote:

>James Stroud wrote:

>>See the documentation for xreadlines.

why?

</F>

5.16 xreadlines -- Efficient iteration over a file

http://www.python.org/dev/peps/pep-0004/

The cheat sheet for the effbot quiz :-)

Peter

[stdazi]

lines = open('blah').readlines()
for i in range(0, len(lines)-1) :
print lines[i]

ei***********@yahoo.com wrote:

hi,
how can i skip printing the last line using loops (for /while)

eg

for line in open("file):
print line.

I want to skip printing last line of the file.thanks

[tobiah]

See the documentation for xreadlines.

>
James

Hmm...

This method returns the same thing as iter(f). New in version 2.1.
Deprecated since release 2.3. Use "for line in file" instead.

--
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