Hello i'm a beginner in pythonanywhere.
I'm trying to write to a txt file but it isn't working, this is my code:
write_file = open("/home/Debonnet/test/test.txt", "a")
write_file.write("test2")
write_file.close
But nothing is being written to the file..I tried "w" instead of "a" also but nothing chan
Modern Python prefers the with idiom:
with open("/home/Debonnet/test/test.txt", "w") as f:
f.write("test2")
The with means Python will magically call close for you automatically at the end of the block, even if anything in there throws an exception
On "w" vs "a", the latter means "append", so it won't overwrite previous contents...
close is a method. You need to call it like this: write_file.close()
Related
Thanks to this great answer from #Przemyslaw Szufel, we can easily redirect stdio output into a file providing its path.
I wanted to know if it is possible to both redirect stio output to a file and still continue print it in the terminal. That is probably an easy feature to achieve but I could not find it!
And obviously not running the code twice :)
You need a Tee Stream such as https://github.com/fredrikekre/TeeStreams.jl/.
Unfortunately the interface of redirect_stdio does not accept abstract IO for its sink. It requires it to be an IOStream which is a concrete Julia type.
So it seems like there is no good way with the redirect_stdio via streams.
However redirect_stdio does accept sockets and named pipes and this is a way you could consider (yet too complex for this simple tasks - maybe someone finds a more elegant solution).
First you need to create a pipe server that will be running asynchronously in your REPL session (this is code for Windows for Linux you will probably need to remove \\.\pipe\ from the pipe name):
using Sockets
srv = Sockets.listen(raw"\\.\pipe\TeePipe")
mystdout = stdout
#async begin
open("log.txt", "w") do f
sock = accept(srv)
while !eof(sock)
line = readline(sock)
println(mystdout, line)
flush(mystdout)
println(f, line)
flush(f)
end
end
end
Now at the same REPL session you create the client:
teelogger = Sockets.connect(raw"\\.\pipe\TeePipe")
And here is a sample REPL session showing that this works:
julia> redirect_stdio(stdout=teelogger) do
println("Line1")
println("Line2")
#show 3+4
end
Line1
Line2
3 + 4 = 7
7
shell> more log.txt
Line1
Line2
3 + 4 = 7
I am writing a script that can execute a batch file, which needs to open a file in the same folder first. My current code is:
from subprocess import Popen
p = Popen("Mad8dl.bat <RUNTHISTO.txt>", cwd=r"C:\...\test")
stdout, stderr = p.communicate()
where the ... is just the path to the folder. However, everytime I run it I get the syntax error:
The syntax of the command is incorrect
Any help regarding the syntax would be greatly appreciated.
First, you should probably remove the < and > angle brackets from your code; just pass the filename, without any brackets, to your batch file. (Unless your filename really does contain < and > characters, in which case I really want to know how you managed it since those characters are forbidden in filenames in Windows).
Second, your code should look like:
from subprocess import Popen, PIPE
p = Popen(["Mad8dl.bat", "RUNTHISTOO.txt"], cwd=r"C:\...\test", stdout=PIPE, stderr=PIPE)
stdout, stderr = p.communicate()
Note the list containing the components of the call, rather than a single string. Also note that you need to specify stdout=PIPE and stderr=PIPE in your Popen() call if you want to use communicate() later on.
I'm trying to solve the bilateral problem on Spotify's Tech Puzzles. http://www.spotify.com/us/jobs/tech/bilateral-projects/ I have something that is working on my computer that reads input from a file input.txt, and it outputs to ouput.txt. My problem is that I cannot figure out how to make my code work when I submit it where it must read from stdin. I have looked at several other posts and I don't see anything that makes sense to me. I see some people just use raw_input - but this produces a user prompt?? Not sure what to do. Here is the protion of my code that is suposed to read the input, and write the output. Any suggestions on how this might need changed? Also how would I test the code once it is changed to read from stdin? How can I put test data in stdin? The error i get back from spotify says Run Time Error - NameError.
import sys
# Read input
Input = []
for line in sys.stdin.readlines():
if len(line) <9:
teamCount = int(line)
if len(line) > 8:
subList = []
a = line[0:4]
b = line[5:9]
subList.append(a)
subList.append(b)
Input.append(subList)
##### algorithm here
#write output
print listLength
for empWin in win:
print empWin
You are actually doing ok.
for line in sys.stdin.readlines():
will read lines from stdin. It can however be shortened to:
for line in sys.stdin:
I don't use Windows, but to test your solution from a command line, you should run it like this:
python bilateral.py < input.txt > output.txt
If I run your code above like that, I see the error message
Traceback (most recent call last):
File "bilateral.py", line 20, in <module>
print listLength
NameError: name 'listLength' is not defined
which by accident (because I guess you didn't send in that) was the error the Spotify puzzle checker discovered. You have probably just misspelled a variable somewhere.
I'm fairly new to Perl and have been searching the interwebs for documentation for what I'm trying to do. I'm not having any luck.
I have a program that outputs information to stdout with prompts throughout. I need to make a Perl script to pipe that information to a file.
I thought I could use Expect but there seems to be a problem with the pipe after the first prompt.
Here is the part of my code:
# Run program and compare the output to the BASE file
$cmd = "./program arg1 arg2 arg3 arg4 > $outfile";
my $exp = new Expect;
$exp->spawn($cmd);
BAIL_OUT("couldn't create expect object") if (! defined $exp);
$exp->expect(2);
$exp->send("\n");
For this case there is only a single prompt for the user to press "enter". This program is small and very fast - 2 seconds is plenty of time to reach the first prompt.
The output file only contains the first half of the information.
Does anyone have any suggestions on how I can grab the second half as well?
UPDATE:
I've verified that this works with Expect by using a simple script:
spawn ./program arg1 arg2 arg3 arg4
expect "<Return>"
send "\r"
interact
Where "< Return >" is a verbose expression that the Perl script could look for.
Note: I've tried writing my Perl script to expect "< Return >"...it makes no difference.
i.e.
$exp->expect(2, '-re', "<Return>")
Any thoughts?
UPDATE2:
Hazaah! I've found a solution to my problem...completely by accident.
So, I had a mistype in some test code I made...
$exp->expect(2);
$exp->send("\r");
$exp->expect(2);
Note the trailing expect(2)...I accidentally left that in and it worked!
So, I'm trying to understand what is happening. Unix expect does not seem work this way! It appears Expect implemented in Perl "expects" anything...not just prompts?
So, I provided expect another 2 seconds to collect stdout and I am able to get everything.
If anyone can offer some more detailed information as to what is going on here I'd love to understand what is going on.
Try sending \r instead of \n - you're trying to emulate a carriage return, not a newline, and the tty settings might not be translating them.
ALSO:
A suggestion from the Expect docs FAQ section, which seems likely given your accidental solution:
My script fails from time to time without any obvious reason. It
seems that I am sometimes loosing output from the spawned program.
You could be exiting too fast without giving the spawned program
enough time to finish. Try adding $exp->soft_close() to terminate the
program gracefully or do an expect() for 'eof'.
Alternatively, try adding a 'sleep 1' after you spawn() the program.
It could be that pty creation on your system is just slow (but this is
rather improbable if you are using the latest IO-Tty).
Standard unix/tcl expect doesn't exit in interactive mode, which could give your program enough time to finish running.
It's been a while since I've used Expect, but I'm pretty sure you need to provide something for Expect to match the prompt against:
$exp->expect( 2, 'Press enter' );
for example.
I have written a shebang R script and would like to execute it from a Perl script. I currently use system ($my_r_script_path, $r_script_arg1, $r_script_arg2, ...) and my question is how can I verify the R script terminates normally (no errors or warnings).
guess I should make my R script return some true value at the end, only if everything is OK, then catch this value in Perl, but I'm not sure how to do that.
Thanks!
You can set the return value in the command quit(), eg q(status=1). Default is 0, see also ?quit. How to catch that one in Perl, is like catching any other returning value in Perl. It is saved in a special variable $? if I remember right. See also the examples in the perldoc for system, it should be illustrated there.
On a sidenote, I'd just use the R-Perl interface. You can find info and examples here :
http://www.omegahat.org/RSPerl/
Just for completeness :
At the beginning of your script, you can put something like :
options(
warn=2, # This will change all warnings into errors,
# so warnings will also be handled like errors
error= quote({
sink(file="error.txt"); # save the error message in a file
dump.frames();
print(attr(last.dump,"error.message"));
sink();
q("no",status=1,FALSE) # standard way for R to end after errors
})
)
This will save the error message, and break out of the R session without saving, with exit code 1 and without running the .Last.
Still, the R-Perl interface offers a lot more possibilities that are worth checking out if you're going to do this more often.