File Handling Problems Python I/O

[Josh]

Hi,

I am having a problem with Python. I am new to Python as a programming
language, but I do have experience in other languages. I am
experiencing strange problems with File handling and wonder if anyone
else has seen this or knows what I am doing wrong. I am simply trying
to open a file for read and iterate through until the end of file. I am
able to do so without a problem, but here's the catch: The open
statement is only working on certain files. I open a simple text file
say file1.txt without any issues, but I change the open statement to
another text file and it error's out stating the file doesn't exist. I
know the code is correct because it worked for the other file. I have
tried both binary and ascii modes to no avail. Any idea why this is
happening? I am running Python 2.3.4 wxPython 2.5.3.1 and SPE as the
IDE on Win2k. Thanks

Josh

[Peter Hansen]

Josh wrote:

He is the function where I am making the call. If I change the open
statment to another file, say "c:\test.tx t", a file I know exists, it
will error out stating the file does not exist. Thanks

def GetStartVars(se lf):
try:
DOWNFILE = open("c:\fixes. txt","r")

Josh, it's surprising that this example worked for you,
given that \f is another string escape (in this case
it's an ASCII FF (formfeed), character code 12, instead
of the TAB (code 8) character that c:\test.txt gives you.

Are you sure this was one of the names that worked?

BTW, the following link in the docs provides a list of
all the recognized escape sequences:

http://www.python.org/doc/current/ref/strings.html

-Peter

[Craig Ringer]

On Fri, 2005-01-07 at 02:06, Josh wrote:

Peter,

Thank you for the rookie correction. That was my exact problem. I
changed the address to use forward slashes and it works perfect. I did
not know that a backslash had special meaning within a string, but now
I do! Thanks again

There's another common mistake you might want to head off now, too.
Consider the following program:

--------
directory = r"c:\mydata"
datafilename = "something. txt"

datafile = open(directory + datafilename,"r ")
---------

It's very common for this to happen, usually when the paths are
originally written with trailing slashes then changed to not have them
later.

Rather than saying "all paths must have trailing slashes", manually
formatting in slashes, or other platform-specific uglyness, consider
using the os.path module to take care of it:

--------
import os

directory = r"c:\mydata"
datafilename = "something. txt"

datafile = open(os.path.jo in(directory,da tafilename),"r" )
--------

This will work on any platform (so long as the literal paths are
correct) and will work no matter whether or not there are trailing path
separators on the input strings. os.path.join can take more than two
arguments, too.

os.path has lots of other handy tools, so I strongly recommend checking
it out.

--
Craig Ringer