delete first line in a file

[Juergen Huber]

hello,

i am a dummy user in python and new in this programming language and so
there will be questions, that´s for you no problem! i never have before
programmed in any language! sorry for this! i hope you will help me, that i
also could the basics in this language! and later many more, so i hope ! :)

the first question for me in this newsgroup will be the follow one:

- is there a way to delete in a csv-file the first line?!

big thanks, juergen

[Fredrik Lundh]

Re: delete first line in a file

Juergen Huber wrote:
[color=blue]
> i am a dummy user in python and new in this programming language and so
> there will be questions, that´s for you no problem! i never have before
> programmed in any language! sorry for this! i hope you will help me, that i
> also could the basics in this language! and later many more, so i hope ! :)
>
> the first question for me in this newsgroup will be the follow one:
>
> - is there a way to delete in a csv-file the first line?![/color]

in general, modern file systems can only remove and add stuff at the end of a
file, so the only way to do this is to rewrite the entire file.

(you can either load the entire file, fix it up, and write it out again, or copy the
file to a new file, skipping the first line or row).

</F>

[Juergen Huber]

Re: delete first line in a file

Fredrik Lundh wrote:[color=blue]
> Juergen Huber wrote:
>[color=green]
>> i am a dummy user in python and new in this programming language and
>> so there will be questions, that´s for you no problem! i never have
>> before programmed in any language! sorry for this! i hope you will
>> help me, that i also could the basics in this language! and later
>> many more, so i hope ! :)
>>
>> the first question for me in this newsgroup will be the follow one:
>>
>> - is there a way to delete in a csv-file the first line?![/color]
>
> in general, modern file systems can only remove and add stuff at the
> end of a
> file, so the only way to do this is to rewrite the entire file.
>
> (you can either load the entire file, fix it up, and write it out
> again, or copy the file to a new file, skipping the first line or
> row).
>
> </F>[/color]

ok...i thought as much, that i have to copy this file!

how will i do that?!
how will i fix this file => delete the first line?!

with which commands could i do that?!

thanks

[Fredrik Lundh]

Re: delete first line in a file

Juergen Huber wrote:
[color=blue]
> ok...i thought as much, that i have to copy this file!
>
> how will i do that?!
> how will i fix this file => delete the first line?!
>
> with which commands could i do that?![/color]

start here:

http://docs.python.org/tut/node9.html#SECTION009200000000000000000

</F>

[Juergen Huber]

Re: delete first line in a file

Fredrik Lundh wrote:[color=blue]
> Juergen Huber wrote:
>[color=green]
>> ok...i thought as much, that i have to copy this file!
>>
>> how will i do that?!
>> how will i fix this file => delete the first line?!
>>
>> with which commands could i do that?![/color]
>
> start here:
>
> http://docs.python.org/tut/node9.htm...00000000000000
>
> </F>[/color]

that documentation i have already read, but it wouldn`t help me for my
problem!
i know, how i can read the first line an print them on the screen!
but...how can i say python, delete the first line?!
thats my problem!
in the entry of my posting i wrote, that i am a newbie and so please
understand me, that i ask so questions?! :-)

thanks for your help!

[Michele Petrazzo]

Re: delete first line in a file

Juergen Huber wrote:[color=blue]
> but...how can i say python, delete the first line?!
> thats my problem![/color]

You can open the file, read its lines with readlines function ( that
return a list), so make your modifies and save to another file.

Now, do you know how to work with lists?

http://python.org/doc/2.4.2/tut/node5.html#SECTION005140000000000000000

and now you have only to wrote it

http://python.org/doc/2.4.2/tut/node9.html#SECTION009200000000000000000

Michele

[Schüle Daniel]

Re: delete first line in a file

Juergen Huber schrieb:[color=blue]
> Fredrik Lundh wrote:[color=green]
>> Juergen Huber wrote:
>>[color=darkred]
>>> ok...i thought as much, that i have to copy this file!
>>>
>>> how will i do that?!
>>> how will i fix this file => delete the first line?!
>>>
>>> with which commands could i do that?![/color]
>> start here:
>>
>> http://docs.python.org/tut/node9.htm...00000000000000
>>
>> </F>[/color]
>
> that documentation i have already read, but it wouldn`t help me for my
> problem!
> i know, how i can read the first line an print them on the screen!
> but...how can i say python, delete the first line?!
> thats my problem!
> in the entry of my posting i wrote, that i am a newbie and so please
> understand me, that i ask so questions?! :-)
>
> thanks for your help![/color]


simple!

f = file("old.file" )
ignore = f.readline()
file("new.file" , "w+").write(f.r ead())

hth, Daniel

[Fredrik Lundh]

Re: delete first line in a file

Juergen Huber wrote:
[color=blue][color=green]
>> start here:
>>
>> http://docs.python.org/tut/node9.htm...00000000000000[/color]
>
> that documentation i have already read, but it wouldn`t help me for my
> problem![/color]

that documentation and a little experimentation should be all you need.
[color=blue]
> i know, how i can read the first line an print them on the screen!
> but...how can i say python, delete the first line?!
> thats my problem![/color]

read the first line, and ignore it.

then read all the other lines, and write them to a new file.

</F>

[Juergen Huber]

Re: delete first line in a file

this helps me!

thank you very much!!!!!

greetings, juergen



JH> Fredrik Lundh wrote:
[color=blue][color=green]
>> Juergen Huber wrote:[/color][/color]
[color=blue][color=green]
>>[/color][/color]
[color=blue][color=green][color=darkred]
>>> ok...i thought as much, that i have to copy this file![/color][/color][/color]
[color=blue][color=green][color=darkred]
>>>[/color][/color][/color]
[color=blue][color=green][color=darkred]
>>> how will i do that?![/color][/color][/color]
[color=blue][color=green][color=darkred]
>>> how will i fix this file => delete the first line?![/color][/color][/color]
[color=blue][color=green][color=darkred]
>>>[/color][/color][/color]
[color=blue][color=green][color=darkred]
>>> with which commands could i do that?![/color][/color][/color]
[color=blue][color=green]
>>[/color][/color]
[color=blue][color=green]
>> start here:[/color][/color]
[color=blue][color=green]
>>[/color][/color]
[color=blue][color=green]
>> http://docs.python.org/tut/node9.htm...00000000000000[/color][/color]
[color=blue][color=green]
>>[/color][/color]
[color=blue][color=green]
>> </F>[/color][/color]

JH> that documentation i have already read, but it wouldn`t help me for my

JH> problem!

JH> i know, how i can read the first line an print them on the screen!

JH> but...how can i say python, delete the first line?!

JH> thats my problem!

as Fredrik told you, you can not delete the first line directly!!!

JH> in the entry of my posting i wrote, that i am a newbie and so please

JH> understand me, that i ask so questions?! :-)

We are trying to understand that, but it is expected some effort on

your side as well :)

You didn't read the documentation properly!

try to experiment with the code by yourself as well!

Try:

1) open your file

2) use readlines() method

which returns the list of ALL rows from the file and store them to some
variable.

it can be done for example like:

all_lines = f.readlines()

(if you do not know, what the list is, start here:

http://docs.python.org/tut/node5.htm...00000000000000)

4) save the list members without its first member to the file

for example:

for line in all_lines[1:]:

f.write(line)

5) close the file



Good luck

Petr Jakes











JH> thanks for your help!

[Petr Jakeš]

Re[2]: delete first line in a file

JH> this helps me!

JH> thank you very much!!!!!

JH> greetings, juergen
I am happy to see my postings (which I sent by accident to you only, not to
the list, see below) helped. But....:
Its a pity we can not see your solution (your code) here :(
It helps to others as well to see, how to solve some "problems"

Petr Jakes
JH>> that documentation i have already read, but it wouldn`t help me for my
JH>> problem!
JH>> i know, how i can read the first line an print them on the screen!
JH>> but...how can i say python, delete the first line?!
JH>> thats my problem!
PJ> as Fredrik told you, you can not delete the first line directly!!!
JH>> in the entry of my posting i wrote, that i am a newbie and so please
JH>> understand me, that i ask so questions?! :-)
PJ> We are trying to understand that, but it is expected some effort on
PJ> your side as well :)
PJ> You didn't read the documentation properly!
PJ> try to experiment with the code by yourself as well!

PJ> Try:

PJ> 1) open your file
PJ> 2) use readlines() method
PJ> which returns the list of ALL rows from the file and store them to some
PJ> variable.
PJ> it can be done for example like:

PJ> all_lines = f.readlines()

PJ> (if you do not know, what the list is, start here:
PJ> http://docs.python.org/tut/node5.htm...00000000000000)

PJ> 4) save the list members without its first member to the file
PJ> for example:

PJ> for line in all_lines[1:]:
PJ> f.write(line)

PJ> 5) close the file

JH> Good luck
JH> Petr Jakes











JH>> thanks for your help!