Christopher Spears wrote:
I created a script that opens an existing text file,
allows the user to write over the original contents,
and then save the file. The original contents are
then saved in a separate file. Here is the script:
#!/usr/bin/python
'editTextFile.py -- write over contents of existing
text file'
import os, string
# get filename
while True:
fname = raw_input('Enter file name: ')
if not (os.path.exists(fname)):
print*** ERROR: '%s' doesn't exist % fname
else:
break
# get file content (text) lines
all = []
print \nEnter lines ('.' by itself to quit).\n
# loop until user terminates input
while True:
entry = raw_input(' ')
if entry == '.':
break
else:
all.append(entry)
# write lines to file with NEWLINE line terminator
print 1) Replace file's contents
print Any other key quits function without replacing
file's contents
choice = raw_input(Make a choice: )
if choice == '1':
fobj = open(fname, 'r')
fobj_lines = fobj.readlines()
fobj.close()
fobj = open(fname, 'w')
fname_orig = fname + '_orig'
fobj_orig = open(fname_orig, 'w')
stripped_lines = []
for line in fobj_lines:
string.strip(line)
stripped_lines.append(line)
fobj_orig.write('\n'.join(stripped_lines))
fobj_orig.close()
fobj.write('\n'.join(all))
fobj.close()
print 'DONE!'
else:
print 'Bye!'
I took a file called myfile. The original contents of
myfile were:
Hi!
This is my file.
It really rocks!
I then ran my script:
Enter file name: myfile
Enter lines ('.' by itself to quit).
test
test
test
.
1) Replace file's contents
Any other key quits function without replacing file's
contents
Make a choice: 1
DONE!
Now the contents of myfile are:
test
test
test
The original contents were saved in myfile_orig. The
contents of myfile_orig are:
Hi!
This is my file.
It really rocks!
Extra newlines were added. This won't do. I think
the problem lies with
fobj_orig.write('\n'.join(stripped_lines))
However, when I rewrite this line code as
fobj_orig.write(string.join(stripped_lines))
I get
Hi!
This is my file.
It really rocks!
That doesn't work either. Any suggestions?
Before you write to the file, just use one of the os module functions to
rename the original file to the new filename. Then when you go to open
the original file, it'll just create a new one.
The way you're currently doing it now, there's a period where both
file's data is stored in memory, after you've opened both files for
writing. This means that if the program were to crash at some point in
here, you'll lose your original data. This is a pretty big problem for
a text editor :)
As per your original question, we can use reasoning to figure out what
the problem is.
There are extra spaces on every line except the first.
However, there are still newlines.
This means that your original strings must have had newlines.
The spaces are explained by the string.join method.
(Methods of string are deprecated anyway.)
We can deduce that by default string.join uses space as the separation
character.
But by leiu of the example \n.join() we know we can say
somestring.join(strings_to_join) and it will join the strings with
that character in between each string.
.join(stripped_lines) would have the same effect as
string.join(stripped_lines). So what do you do if you don't want any
characters at all separating your strings? Simple: use an empty string:
.join(stripped_lines)
As I mentioned above, there are multiple ways to approach this problem.
One other thing you could do if you wanted the program to be
functionally equivalent is just use writelines() instead of write() and
then you don't have to join the strings.
-Luke
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