Inexplicable behavior in simple example of a set in a class
I have written two EXTREMELY simple python classes. One class (myClass1) contains a data attribute (myNum) that contains an integer. The other class (myClass2) contains a data attribute (mySet) that contains a set. I instantiate 2 instances of myClass1 (a & b). I then change the value of a.myNum. It works as expected. Then I instantiate 2 instances of myClass2 (c & d). I then change the value of c.mySet. Bizarrely changing the value of c.mySet also affects the value of d.mySet which I haven't touched at all!?!?! Can someone explain this very strange behavior to me? I can't understand it for the life of me. Please see below the source code as well as the output. -- SOURCE CODE -- import sets class myClass1: myNum = 9 def clearNum(self): self.myNum = 0 def __str__(self): return str(self.myNum) class myClass2: mySet = sets.Set(range(1,10)) def clearSet(self): self.mySet.clear() def __str__(self): return str(len(self.mySet)) if __name__ == "__main__": # Experiment 1. Modifying values of member integers in two different instances of a class # Works as expected. a = myClass1() b = myClass1() print "a = %s" % str(a) print "b = %s" % str(b) print "a.clearNum()" a.clearNum() print "a = %s" % str(a) print "b = %s\n\n\n" % str(b) # Experiment 2. Modifying values of member sets in two different instances of a class # Fails Unexplicably. d is not being modified. Yet calling c.clearSet() seems to change d.mySet's value c = myClass2() d = myClass2() print "c = %s" % str(c) print "d = %s" % str(d) print "c.clearSet()" c.clearSet() print "c = %s" % str(c) print "d = %s" % str(d) -- OUTPUT -- > python.exe myProg.py a = 9 b = 9 a.clearNum() a = 0 b = 9 c = 9 d = 9 c.clearSet() c = 0 d = 0 -- http://mail.python.org/mailman/listinfo/python-list
Re: Inexplicable behavior in simple example of a set in a class
> Instance variables are properly created in the __init__() > initializer method, *not* directly in the class body. > > Your class would be correctly rewritten as: > > class MyClass2(object): > def __init__(self): > self.mySet = sets.Set(range(1,10)) > > def clearSet(self): > # ...rest same as before... Thanks Chris. That was certainly very helpful!! So just out of curiosity, why does it work as I had expected when the member contains an integer, but not when the member contains a set? -- http://mail.python.org/mailman/listinfo/python-list
Need help with really elementary pexpect fragment
I want to write a pexpect script that simply cd's into a directory ("~/
install") and then runs a command from there. It should be so easy.
But even my cd command is failing. Can't figure out what the problem
is. The command line prompt is "[my machine name here] % "
Here is the code fragment:
print "Spawning Expect"
p = pexpect.spawn ('/bin/tcsh',)
print "Sending cd command"
i = p.expect([pexpect.TIMEOUT, "%",])
assert i != 0, "Time-Out exiting"
p.sendline("cd ~/install")
Here is the output:
Spawning Expect
Sending cd command
Time-Out exiting
How could I be screwing something so simple up??
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Re: Need help with really elementary pexpect fragment
Oops! Good call.
Thank you. You pointed out my mistake.
- Saqib
On Tue, Dec 20, 2011 at 12:31 AM, Nick Dokos wrote:
> Saqib Ali wrote:
>
> >
> > I want to write a pexpect script that simply cd's into a directory ("~/
> > install") and then runs a command from there. It should be so easy.
> > But even my cd command is failing. Can't figure out what the problem
> > is. The command line prompt is "[my machine name here] % "
> >
> > Here is the code fragment:
> >
> > print "Spawning Expect"
> > p = pexpect.spawn ('/bin/tcsh',)
> >
>
> If you execute /bin/tcsh by hand, do you get a "%" prompt?
>
> Nick
>
> > print "Sending cd command"
> > i = p.expect([pexpect.TIMEOUT, "%",])
> > assert i != 0, "Time-Out exiting"
> > p.sendline("cd ~/install")
> >
> > Here is the output:
> >
> > Spawning Expect
> > Sending cd command
> > Time-Out exiting
> >
> >
> > How could I be screwing something so simple up??
> > --
> > http://mail.python.org/mailman/listinfo/python-list
> >
>
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Can I get use pexpect to control this process?
I have a program X that constantly spews output, hundreds of lines per minute. X is not an interactive program. IE: it doesn't take any user input. It just produces a lot of textual output to STDOUT. I would like to save the output produced by X into a different file every 5 seconds regardless of the actual content. I want one file to contain the output from seconds 0-5, another file should contain 6-10, etc. etc. Can I do this with pexpect? I'm not sure I can because the "before" argument gives me EVERYTHING upto the most recent match. What I really need is something that will give me what was produced between the last 2 calls to pexpect.expect(). -- http://mail.python.org/mailman/listinfo/python-list
Can't I define a decorator in a separate file and import it?
I'm using this decorator to implement singleton class in python: http://stackoverflow.com/posts/7346105/revisions The strategy described above works if and only if the Singleton is declared and defined in the same file. If it is defined in a different file and I import that file, it doesn't work. Why can't I import this Singleton decorator from a different file? What's the best work around? -- http://mail.python.org/mailman/listinfo/python-list
Re: Can't I define a decorator in a separate file and import it?
MYCLASS.PY: #!/usr/bin/env python import os, sys, string, time, re, subprocess import Singleton @Singleton class myClass: def __init__(self): print 'Constructing myClass' def __del__(self): print 'Destructing myClass' SINGLETON.PY: #!/usr/bin/env python import os, sys, string, time, re, subprocess import Singleton @Singleton class myClass: def __init__(self): print 'Constructing myClass' def __del__(self): print 'Destructing myClass' TRACEBACK: >>> import myClass Traceback (most recent call last): File "", line 1, in File "myClass.py", line 6, in @Singleton TypeError: 'module' object is not callable - Saqib >> > Post the code, and the traceback. > > ~Ethan~ -- http://mail.python.org/mailman/listinfo/python-list
Re: Can't I define a decorator in a separate file and import it?
BTW Here is the traceback: >>> import myClass Traceback (most recent call last): File "", line 1, in File "myClass.py", line 6, in @Singleton TypeError: 'module' object is not callable Here is Singleton.py: class Singleton: def __init__(self, decorated): self._decorated = decorated def Instance(self): try: return self._instance except AttributeError: self._instance = self._decorated() return self._instance def __call__(self): raise TypeError( 'Singletons must be accessed through the `Instance` method.') Here is myClass.py: #!/usr/bin/env python import os, sys, string, time, re, subprocess import Singleton @Singleton class myClass: def __init__(self): print 'Constructing myClass' def __del__(self): print 'Destructing myClass' -- http://mail.python.org/mailman/listinfo/python-list
Re: Can't I define a decorator in a separate file and import it?
Thanks for pointing out the mistake! Works. - Saqib On Thu, Dec 22, 2011 at 4:31 PM, Ethan Furman wrote: > Saqib Ali wrote: > >> MYCLASS.PY: >> >> #!/usr/bin/env python >> import os, sys, string, time, re, subprocess >> import Singleton >> > > This should be 'from Singleton import Singleton' > > > > @Singleton >> class myClass: >>def __init__(self): >>print 'Constructing myClass' >> > > At this point, the *instance* of myClass has already been constructed and > it is now being initialized. The __new__ method is where the instance is > actually created. > > > >>def __del__(self): >>print 'Destructing myClass' >> >> >> > class Singleton: > > > > def __init__(self, decorated): > > self._decorated = decorated > > > > def Instance(self): > > try: > > return self._instance > > except AttributeError: > > self._instance = self._decorated() > > return self._instance > > > > def __call__(self): > > raise TypeError( > > 'Singletons must be accessed through the `Instance` > > method.') > > > ~Ethan~ > -- http://mail.python.org/mailman/listinfo/python-list
Changing the system clock with pexpect confuses pexpect!
See my code below.
I'm controlling a shell logged in as root with pexpect.
The class below has a method (startProc) which spawns a shell and
keeps it alive until told to destroy it (stopProc).
The other 2 methods in this class allow me to change the system clock
and to get the IP Address of this machine.
They all work fine except when I advance the system clock, and
then try to get the IP Address.
In that case, I get an exception because pexpect incorrectly thinks
the output it is getting from ifconfig is invalid. But it is not.
Pexpect is just confused. This doesn't happen when I move the clock
backwards. It only happens when I move the clock forward.
I believe what is going on is that internally pexpect uses the system
clock to keep track of when it receives data from spawned processes.
When I mess with the clock, that messes up the internal workings of
pexpect.
Any suggestions what I should do? I have numerous concurrent pexpect
processes running when I modify the clock. Is there anyway to prevent
them all from getting totally screwed up??
-
#!/usr/bin/env python
import pexpect, os, time, datetime, re
def reportPrint(string):
print string
def reportAssert(condition, string)
if condition == False:
print string
raise Exception
class rootManager:
rootProc = None
rootPrompt = "] % "
myPrompt = "] % "
def __init__(self):
pass
def startProc(self):
if self.rootProc != None:
reportPrint("\t\t- Root Process is already created")
else:
self.rootProc = pexpect.spawn ('/bin/tcsh',)
i = self.rootProc.expect([pexpect.TIMEOUT,
self.myPrompt,])
reportAssert(i != 0, "Time-Out exiting")
reportPrint("\t\t- Sending su")
self.rootProc.sendline("su")
i = self.rootProc.expect([pexpect.TIMEOUT, "Password: ",])
reportAssert(i != 0, "Time-Out exiting")
reportPrint("\t\t- Sending Password")
self.rootProc.sendline(ROOT_PASSWORD)
i = self.rootProc.expect([pexpect.TIMEOUT,
self.rootPrompt,])
reportAssert(i != 0, "Time-Out exiting")
reportPrint("\t\t- Root Process created")
def getIPAddr(self):
reportAssert(self.rootProc != None, "No active Root Process!")
reportPrint("\t\t- Sending ifconfig -a")
self.rootProc.sendline("ifconfig -a")
i = self.rootProc.expect([pexpect.TIMEOUT, self.rootPrompt,])
reportAssert(i != 0, "Time-Out exiting")
outputTxt = self.rootProc.before
ipList = [i for i in re.compile("(?<=inet )\d{1,3}\.\d{1,3}\.
\d{1,3}\.\d{1,3}").findall(outputTxt) if i != "127.0.0.1"]
reportAssert(len(ipList) == 1, "Cannot determine IP Address
from 'ifconfig -a': \n%s" % outputTxt)
return ipList[0]
def changeClock(self, secondsDelta):
reportAssert(self.rootProc != None, "No active Root Process!")
newTime = datetime.datetime.now() +
datetime.timedelta(seconds=secondsDelta)
dateStr = "%02d%02d%02d%02d%s" % (newTime.month, newTime.day,
newTime.hour, newTime.minute, str(newTime.year)[-2:])
reportPrint("\t\t- Sending 'date %s' command" % dateStr)
self.rootProc.sendline("date %s" % dateStr)
#Remember, by changing the clock, you are confusing pexpect's
timeout measurement!
# so ignore timeouts in this case
i = self.rootProc.expect([pexpect.TIMEOUT,
self.rootPrompt,],)
def stopProc(self):
if self.rootProc == None:
reportPrint("\t\t- Root Process is already destroyed")
else:
reportPrint("\t\t- Sending exit command")
rootProc.sendline("exit")
i = rootProc.expect([pexpect.TIMEOUT, self.myPrompt])
reportAssert(i != 0, "Time-Out exiting")
reportPrint("\t\t- Sending exit command")
rootProc.sendline("exit")
i = rootProc.expect([pexpect.TIMEOUT, pexpect.EOF])
reportAssert(i != 0, "Time-Out exiting")
self.rootProc.close()
self.rootProc = None
reportPrint("\t\t- Root Process Destroyed")
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Problem while doing a cat on a tabbed file with pexpect
I am using Solaris 10, python 2.6.2, pexpect 2.4
I create a file called me.txt which contains the letters "A", "B", "C"
on the same line separated by tabs.
My shell prompt is "% "
I then do the following in the python shell:
>>> import pexpect
>>> x = pexpect.spawn("/bin/tcsh")
>>> x.sendline("cat me.txt")
11
>>> x.expect([pexpect.TIMEOUT, "% "])
1
>>> x.before
'cat me.txt\r\r\nA B C\r\n'
>>> x.before.split("\t")
['cat me.txt\r\r\nA B C\r\n']
Now, clearly the file contains tabs. But when I cat it through expect,
and collect cat's output, those tabs have been converted to spaces.
But I need the tabs!
Can anyone explain this phenomenon or suggest how I can fix it?
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Re: Problem while doing a cat on a tabbed file with pexpect
Very good question. Let me explain why I'm not opening me.txt directly
in python with open.
The example I have posted is simplified for illustrative purpose. In
reality, I'm not doing pexpect.spawn("/bin/tcsh"). I'm doing
pexpect.spawn("ssh myuser@ipaddress"). Since I'm operating on a remote
system, I can't simply open the file in my own python context.
On Jan 15, 2:24 pm, Dennis Lee Bieber wrote:
> On Sun, 15 Jan 2012 09:51:44 -0800 (PST), Saqib Ali
>
> wrote:
> >Now, clearly the file contains tabs. But when I cat it through expect,
> >and collect cat's output, those tabs have been converted to spaces.
> >But I need the tabs!
>
> >Can anyone explain this phenomenon or suggest how I can fix it?
>
> My question is:
>
> WHY are you doing this?
>
> Based upon the problem discription, as given, the solution would
> seem to be to just open the file IN Python -- whether you read the lines
> and use split() by hand, or pass the open file to the csv module for
> reading/parsing is up to you.
>
> -=-=-=-=-=-=-
> import csv
> import os
>
> TESTFILE = "Test.tsv"
>
> #create data file
> fout = open(TESTFILE, "w")
> for ln in [ "abc",
> "defg",
> "hijA" ]:
> fout.write("\t".join(list(ln)) + "\n")
> fout.close()
>
> #process tab-separated data
> fin = open(TESTFILE, "rb")
> rdr = csv.reader(fin, dialect="excel-tab")
> for rw in rdr:
> print rw
>
> fin.close()
> del rdr
> os.remove(TESTFILE)
> -=-=-=-=-=-=-
> ['a', 'b', 'c']
> ['d', 'e', 'f', 'g']
> ['h', 'i', 'j', 'A']
> --
> Wulfraed Dennis Lee Bieber AF6VN
> wlfr...@ix.netcom.com HTTP://wlfraed.home.netcom.com/
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Re: Problem while doing a cat on a tabbed file with pexpect
The file me.txt does indeed contain tabs. I created it with vi.
>>> text = open("me.txt", "r").read()
>>> print "\t" in text
True
% od -c me.txt
000 A \t B \t C \n
006
% ls -al me.txt
-rw-r--r-- 1 myUsermyGroup 6 Jan 15 12:42 me.txt
On Jan 15, 6:40 pm, Cameron Simpson wrote:
> On 15Jan2012 23:04, Steven D'Aprano
> wrote:
> | On Sun, 15 Jan 2012 09:51:44 -0800, Saqib Ali wrote:
> | > I am using Solaris 10, python 2.6.2, pexpect 2.4
> | >
> | > I create a file called me.txt which contains the letters "A", "B", "C"
> | > on the same line separated by tabs.
> | [...]
> | > Now, clearly the file contains tabs.
> |
> | That is not clear at all. How do you know it contains tabs? How was the
> | file created in the first place?
> |
> | Try this:
> |
> | text = open('me.txt', 'r').read()
> | print '\t' in text
> |
> | My guess is that it will print False and that the file does not contain
> | tabs. Check your editor used to create the file.
>
> I was going to post an alternative theory but on more thought I think
> Steven is right here.
>
> What does:
>
> od -c me.txt
>
> show you? TABs or multiple spaces?
>
> What does:
>
> ls -ld me.txt
>
> tell you about the file size? Is it 6 bytes long (three letters, two
> TABs, one newline)?
>
> Steven hasn't been explicit about it, but some editors will write spaces when
> you type a TAB. I have configured mine to do so - it makes indentation more
> reliable for others. If I really need a TAB character I have a special
> finger contortion to get one, but the actual need is rare.
>
> So first check that the file really does contain TABs.
>
> Cheers,
> --
> Cameron Simpson DoD#743http://www.cskk.ezoshosting.com/cs/
>
> Yes Officer, yes Officer, I will Officer. Thank you.
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Why does os.stat() tell me that my file-group has no members?
I'm using python 2.6.4 on Solaris 5-10.
I have a file named "myFile". It is owned by someone else, by I ("myuser") am
in the file's group ("mygrp"). Below is my python code. Why does it tell me
that mygrp has no members???
>>> import os, pwd, grp
>>> stat_info = os.stat("myFile")
>>> fileUID = stat_info.st_uid
>>> fileGID = stat_info.st_gid
>>> fileGroup = grp.getgrgid(fileGID)[0]
>>> fileUser = pwd.getpwuid(fileUID)[0]
>>> print "grp.getgrgid(fileGID) = %s" % grp.getgrgid(fileGID)
grp.getgrgid(fileGID) = grp.struct_group(gr_name='mygrp', gr_passwd='',
gr_gid=100, gr_mem=[])
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Re: Why does os.stat() tell me that my file-group has no members?
Thanks!! This was very helpful. It worked perfectly.
I had no clue about the intricacies of how python represents the group data
from the underlying OS.
This page doesn't go into to detailed explanation like you did:
http://docs.python.org/2/library/grp.html
On Wednesday, December 19, 2012 6:17:16 PM UTC-5, Hans Mulder wrote:
> On 19/12/12 22:40:00, saqib.ali...@gmail.com wrote:
>
> >
>
> >
>
> > I'm using python 2.6.4 on Solaris 5-10.
>
> >
>
> > I have a file named "myFile". It is owned by someone else, by
>
> > I ("myuser") am in the file's group ("mygrp"). Below is my python
>
> > code. Why does it tell me that mygrp has no members???
>
> >
>
> >
>
> import os, pwd, grp
>
> stat_info = os.stat("myFile")
>
> fileUID = stat_info.st_uid
>
> fileGID = stat_info.st_gid
>
> fileGroup = grp.getgrgid(fileGID)[0]
>
> fileUser = pwd.getpwuid(fileUID)[0]
>
> print "grp.getgrgid(fileGID) = %s" % grp.getgrgid(fileGID)
>
> >
>
> > grp.getgrgid(fileGID) = grp.struct_group(gr_name='mygrp', gr_passwd='',
> > gr_gid=100, gr_mem=[])
>
>
>
> It doesn't say that your group has no members.
>
>
>
> Every account has a primary group, and some accounts also
>
> have addtional groups. The primary group is the one in the
>
> .pw_gid attribute in the pwd entry. The additional groups
>
> are those that mention the account in the .gr_mem attribute
>
> in their grp entry.
>
>
>
> Your experiment shows that nobody has "mygrp" as an additional
>
> group. So if you're a member of mygrp, then it must be your
>
> primary group, i.e. os.getgid() should return 100 for you.
>
>
>
> You can get a complete list of members of group by adding
>
> two lists:
>
>
>
> def all_members(gid):
>
> primary_members = [ user.pw_name
>
> for user in pwd.getpwall() if user.pw_gid == gid ]
>
> additional_members = grp.getgrgid(gid).gr_mem
>
> return primary_members + additional_members
>
>
>
>
>
> Hope this helps,
>
>
>
> -- HansM
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Why is pexpect acting funny with sendline() and expect()?
I am running Solaris 5-10, python 2.6.2 and pexpect 2.4
I have the very simple python script below which exercises the functionality of
sending and receiving text from the shell.
My understanding is that pexepect([pexpect.TIMEOUT, x,y,z], timeout=w) will
return the index of the match that it found *since the last time pexpect was
called*, but if it takes longer than w seconds, it will return 0.
Here is my very simple script:
#!/usr/bin/env python
import pexpect
myPrompt = " % "
myShell = pexpect.spawn("/bin/tcsh")
print "Sending 'JUNK-0' to shell"
x = myShell.sendline("JUNK-0")
y = myShell.expect([pexpect.TIMEOUT], timeout=1)
print "y = %s" % y
print myShell.before
print "=" * 80
print "\n\n"
for i in range(2):
print "i = %d" % (i+1)
print "Sending 'JUNK-%d' to shell" % (i+1)
x = myShell.sendline("JUNK-%d" % (i+1))
y = myShell.expect([pexpect.TIMEOUT, myPrompt], timeout=10)
print "y = %s" % y
print myShell.before
print "=" * 80
print "\n\n"
FYI, my shell prompt is "myMachine % ", however in this script I have simply
used " % " to keep it generic.
When I run it, I see the following output:
Sending 'JUNK-0' to shell
y = 0
JUNK-0
myMachine % JUNK-0
JUNK-0: Command not found.
myMachine %
i = 1
Sending 'JUNK-1' to shell
y = 1
JUNK-0
myMachine
i = 2
Sending 'JUNK-2' to shell
y = 1
JUNK-0
JUNK-0: Command not found.
myMachine
Why do I see "JUNK-0" consistently recurring in the output? It should be
consumed by the first myShell.expect() statement, but it keeps showing up. Why??
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