Delete first line from file

[Tor Erik Sønvisen]

Hi

How can I read the first line of a file and then delete this line, so that
line 2 is line 1 on next read?

regards

 

[Peter Nuttall]

Hi

How can I read the first line of a file and then delete this line, so that
line 2 is line 1 on next read?

regards

I think you can do something like:

n=false
f=file.open("") #stuff here
g=[]
for line in f.readlines():
if n: g.append(line)
n=true

#write g to file

if you are on a unix box, then using the standard untils might be a
better idea.

Pete

 

[Pieter Claerhout]

what about the following?

f = open( 'file.txt', 'r' )
lines = f.readlines()
f.close()

f = open( 'file.txt'.'w' )
f.write( '\n'.join( lines[1:] ) )
f.close()

cheers,


pieter

Hi

How can I read the first line of a file and then delete this line, so that
line 2 is line 1 on next read?

regards

I think you can do something like:

n=false
f=file.open("") #stuff here
g=[]
for line in f.readlines():
if n: g.append(line)
n=true

#write g to file

if you are on a unix box, then using the standard untils might be a
better idea.

Pete

 

[Jeff Sandys]

You describe the standard behavior, unless you close the file,
is that what you want to do; open file, read line 1, close file,
then open file, read line 2, close file? The other suggestions
here destory content, do you want that?
'line three\n'

 

[Jeff Sandys]

Here is a non-destructive way keeping track of the
current file position when closing the file and
re-open the file where you left off. You can
always use seek(0) to go back to the beginning.

# ---------------------- start of myfile class
class myfile(file):
myfiles = {}
def __init__(self, fname, *args):
file.__init__(self, fname, *args)
if self.name in myfile.myfiles:
pos = myfile.myfiles[fname]
else:
pos = 0
return self.seek(pos)
def close(self):
myfile.myfiles[self.name] = self.tell()
file.close(self)
# ------------------------ end of myfile class

Below is an example with a simple four line file.

PythonWin 2.3.3 (#51, Dec 18 2003, 20:22:39) [MSC v.1200 32 bit (Intel)]
on win32.
Portions Copyright 1994-2001 Mark Hammond ([email protected]) -
see 'Help/About PythonWin' for further copyright information.

f = open("C:/Pydev/test.txt")
f.readlines() ['line one\n', 'line two\n', 'line three\n', 'last line\n']
### short four line file
f.close()
from myfile import myfile
f = myfile("C:/Pydev/test.txt")
f.readline() 'line one\n'
f.readline() 'line two\n'
f.close()
### test, is the file really closed?
f.readline()

Traceback (most recent call last):

This turned out really cool,
thanks for the good question,
Jeff Sandys