* Zeynel:
* Zeynel:
* Zeynel:
Hello,
I've been studying the official tutorial, so far it's been fun, but
today I ran into a problem with the write(). So, I open the file pw
and write "hello" and read:
f = open("pw", "r+")
f.write("hello")
f.read()
But read() returns a bunch of what looks like meta code:
"ont': 1, 'center_insert_even\xc4\x00K\x02\xe8\xe1[\x02z\x8e
\xa5\x02\x0b
\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0 0'QUEUE'\np1\n
(S'exec' ....
What am I doing wrong? Thank you.
After the 'write' the current position in the file is after the "hello", so
reading will read further content from there.
The following works (disclaimer: I'm utter newbie in Python, and didn't consult
the documentation, and it's the first time I've seen the Python 'open'):
f = open("pw", "r+")
f.write( "hello" )
f.seek( 0 ) # Go back to start of file
f.read()
f.close()
Cheers & hth.,
- Alf
Thanks, but it didn't work for me. I still get the meta file. Although
I see that "hello" is there.
Just a thought: try "w+" instead of "r+".
Because if you do
print( open.__doc__ )
as I recall it said something about "w" truncating the file?
Cheers & hth.,
- Alf
No
I still got the same thing.
Hm. Now I had to look in the docs because I thought I'd given bad advice.
Doc of 'open' says:
"The mode 'w+' opens and truncates the file to 0 bytes, while 'r+' opens the
file without truncation."
So with 'w+' the only way to get garbage is if 'read' reads beyond the end of
file, or 'open' doesn't conform to the documentation.
Testing with Python 3.1.1 under Windows XP Pro:
<example>
>>> f = open( "zilly", "w+" )
>>> f.write( "garbagegarbagegarbagegarbagegarbagegarbagegarbagegarbagegarbage" )
63
>>> f.close()
>>> f = open( "zilly", "r" )
>>> f.read()
'garbagegarbagegarbagegarbagegarbagegarbagegarbagegarbagegarbage'
>>> f.close()
>>> f.open( "zilly", "r+" )
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: '_io.TextIOWrapper' object has no attribute 'open'
>>> open( "zilly", "r+" )
<_io.TextIOWrapper name='zilly' encoding='cp1252'>
>>> f = open( "zilly", "r+" )
>>> f.write( "hello" )
5
>>> f.seek( 0 )
0
>>> f.read()
'hellogegarbagegarbagegarbagegarbagegarbagegarbagegarbagegarbage'
>>> f.close()
>>> f = open( "zilly", "w+" )
>>> f.write( "hello" )
5
>>> f.seek( 0 )
0
>>> f.read()
'hello'
>>> f.close()
>>>
</example>
The "w+" works here. Even if I made a typing mistake and apparently left the
file open in the middle there.
Cheers & hth.,
- Alf
