A deranged child has trapped their parents (who are pigs apparently???) in a nightmare labyrinth of cardboard and toys. To find each other in the maze, the players must communicate about what they've seen and where they've gone in this strange maze. MS Windows, Mac OS X, Web browser with special plugins or packaged. 'THE PARENT TRAP'! Harley has faced every challenge even she could possibly imagine, but can she survive.a visit from her parents?! And in 'Harley Loves Joker' part eight, the duo's new headquarters comes with some unforeseen complications!
- Brian Keith, Actor: The Parent Trap. Son of character actor Robert Keith and stage actress Helena Shipman. He grew up on the road with his parents while they toured in plays. First appeared at age 3 in film Pied Piper Malone (1924) with his father. Began acting in radio programs and on stage before World War II. Joined the Marines and served as a machine gunner.
- The Parent Trap (1998) on IMDb: Plot summary, synopsis, and more. —Julian Reischl mac.com Hallie Parker and Annie James are identical twins separated at a young age because of their parents' divorce. Unknowingly to their parents, the girls are sent to the same summer camp where they meet, discover the truth.
| Purpose: | Start and communicate with additional processes. |
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The subprocess module supports three APIs for working withprocesses. The run() function, added in Python 3.5, is ahigh-level API for running a process and optionally collecting itsoutput. The functions call(), check_call(), andcheck_output() are the former high-level API, carried over fromPython 2. They are still supported and widely used in existingprograms. The class Popen is a low-level API used to buildthe other APIs and useful for more complex process interactions. Theconstructor for Popen takes arguments to set up the newprocess so the parent can communicate with it via pipes. It providesall of the functionality of the other modules and functions itreplaces, and more. The API is consistent for all uses, and many ofthe extra steps of overhead needed (such as closing extra filedescriptors and ensuring the pipes are closed) are 'built in' insteadof being handled by the application code separately.
The subprocess module is intended to replace functions such asos.system(), os.spawnv(), the variations of popen()in the os and popen2 modules, as well as thecommands() module. To make it easier to comparesubprocess with those other modules, many of the examples inthis section re-create the ones used for os and popen2.
Note
The API for working on Unix and Windows is roughly the same, butthe underlying implementation is different because of thedifference in process models in the operating systems. All of theexamples shown here were tested on Mac OS X. Behavior on anon-Unix OS may vary.
Running External Command¶
To run an external command without interacting with it in the same wayas os.system(), use the run() function.
The command line arguments are passed as a list of strings, whichavoids the need for escaping quotes or other special characters thatmight be interpreted by the shell. run() returns aCompletedProcess instance, with information about the processlike the exit code and output.
Setting the shell argument to a true value causes subprocessto spawn an intermediate shell process which then runs thecommand. The default is to run the command directly.
Using an intermediate shell means that variables, glob patterns, andother special shell features in the command string are processedbefore the command is run.
Note Death gate mac os.
Using run() without passing check=True is equivalent tousing call(), which only returned the exit code from theprocess.
Error Handling¶
The returncode attribute of the CompletedProcess is theexit code of the program. The caller is responsible for interpretingit to detect errors. If the check argument to run() isTrue, the exit code is checked and if it indicates an errorhappened then a CalledProcessError exception is raised.
The false command always exits with a non-zero status code,which run() interprets as an error.
Note
Passing check=True to run() makes it equivalent to usingcheck_call().
Capturing Output¶
Parent Trap Ost
The standard input and output channels for the process started byrun() are bound to the parent's input and output. That meansthe calling program cannot capture the output of the command. PassPIPE for the stdout and stderr arguments to capturethe output for later processing.
The ls-1 command runs successfully, so the text it prints tostandard output is captured and returned.
Note
Passing check=True and setting stdout to PIPE isequivalent to using check_output().
The next example runs a series of commands in a sub-shell. Messages aresent to standard output and standard error before the commands exitwith an error code.
The message to standard error is printed to the console, but themessage to standard output is hidden.
To prevent error messages from commands run throughrun() from being written to the console, set thestderr parameter to the constant PIPE.
This example does not set check=True so the output of the commandis captured and printed.
To capture error messages when using check_output(), setstderr to STDOUT, and the messages will be merged withthe rest of the output from the command.
The order of output may vary, depending on how buffering is applied tothe standard output stream and how much data is being printed.
Suppressing Output¶
For cases where the output should not be shown or captured, useDEVNULL to suppress an output stream. This example suppressesboth the standard output and error streams.
The name DEVNULL comes from the Unix special device file,/dev/null, which responds with end-of-file when opened for readingand receives but ignores any amount of input when writing.
Working with Pipes Directly¶
The functions run(), call(), check_call(), andcheck_output() are wrappers around the Popen class.Using Popen directly gives more control over how the commandis run, and how its input and output streams are processed. Forexample, by passing different arguments for stdin, stdout, andstderr it is possible to mimic the variations of os.popen().
One-way Communication With a Process¶
To run a process and read all of its output, set the stdout value toPIPE and call communicate().
This is similar to the way popen() works, except that thereading is managed internally by the Popen instance.
To set up a pipe to allow the calling program to write data to it, setstdin to PIPE.
To send data to the standard input channel of the process one time,pass the data to communicate(). This is similar to usingpopen() with mode 'w'.
Parent Trap Mac Os Download
Bi-directional Communication With a Process¶
To set up the Popen instance for reading and writing at thesame time, use a combination of the previous techniques.
This sets up the pipe to mimic popen2().
Capturing Error Output¶
It is also possible watch both of the streams for stdout and stderr,as with popen3().
Reading from stderr works the same as with stdout. PassingPIPE tells Popen to attach to the channel, andcommunicate() reads all of the data from it before returning.
Combining Regular and Error Output¶
To direct the error output from the process to its standard outputchannel, use STDOUT for stderr instead of PIPE.
Combining the output in this way is similar to how popen4()works.
Connecting Segments of a Pipe¶
Multiple commands can be connected into a pipeline, similar to theway the Unix shell works, by creating separate Popeninstances and chaining their inputs and outputs together. Thestdout attribute of one Popen instance is used as thestdin argument for the next in the pipeline, instead of the constantPIPE. The output is read from the stdout handle forthe final command in the pipeline.
The example reproduces the command line:
The pipeline reads the reStructuredText source file for this sectionand finds all of the lines that include other files, then prints thenames of the files being included.
Interacting with Another Command¶
All of the previous examples assume a limited amount ofinteraction. The communicate() method reads all of the outputand waits for child process to exit before returning. It is alsopossible to write to and read from the individual pipe handles used bythe Popen instance incrementally, as the program runs. Asimple echo program that reads from standard input and writes tostandard output illustrates this technique.
The script repeater.py is used as the child process in the nextexample. It reads from stdin and writes the values to stdout, oneline at a time until there is no more input. It also writes a messageto stderr when it starts and stops, showing the lifetime ofthe child process.
The next interaction example uses the stdin and stdoutfile handles owned by the Popen instance in differentways. In the first example, a sequence of five numbers are written tostdin of the process, and after each write the next line ofoutput is read back. In the second example, the same five numbers arewritten but the output is read all at once usingcommunicate().
The 'repeater.py:exiting' lines come at different points in theoutput for each loop style.
Signaling Between Processes¶
The process management examples for the os module include ademonstration of signaling between processes using os.fork() andos.kill(). Since each Popen instance provides a pidattribute with the process id of the child process, it is possible todo something similar with subprocess. The next example combinestwo scripts. This child process sets up a signal handler for theUSR signal.
This script runs as the parent process. It startssignal_child.py, then sends the USR1 signal.
The output is:
Process Groups / Sessions¶
If the process created by Popen spawns sub-processes, thosechildren will not receive any signals sent to the parent. That meanswhen using the shell argument to Popen it will be difficultto cause the command started in the shell to terminate by sendingSIGINT or SIGTERM.
The pid used to send the signal does not match the pid of the child ofthe shell script waiting for the signal, because in this example thereare three separate processes interacting:
- The program
subprocess_signal_parent_shell.py - The shell process running the script created by the main pythonprogram
- The program
signal_child.py
To send signals to descendants without knowing their process id, use aprocess group to associate the children so they can be signaledtogether. The process group is created with os.setpgrp(),which sets process group id to the process id of the current process.All child processes inherit their process group from their parent, andsince it should only be set in the shell created by Popenand its descendants, os.setpgrp() should not be called in thesame process where the Popen is created. Instead, thefunction is passed to Popen as the preexec_fn argument soit is run after the fork() inside the new process, before ituses exec() to run the shell. To signal the entire processgroup, use os.killpg() with the pid value from thePopen instance.
The sequence of events is
- The parent program instantiates
Popen. - The
Popeninstance forks a new process. - The new process runs
os.setpgrp(). - The new process runs
exec()to start the shell. - The shell runs the shell script.
- The shell script forks again and that process execs Python.
- Python runs
signal_child.py. - The parent program signals the process group using the pid of the shell.
- The shell and Python processes receive the signal.
- The shell ignores the signal.
- The Python process running
signal_child.pyinvokes the signal handler.
See also
os– Althoughsubprocessreplaces many of them, thefunctions for working with processes found in theosmodule are still widely used in existing code.- UNIX Signals and Process Groups– A good description of Unix signaling and how process groupswork.
signal– More details about using thesignalmodule.- Advanced Programming in the UNIX(R) Environment– Covers working with multiple processes, such as handlingsignals, closing duplicated file descriptors, etc.
pipes– Unix shell command pipeline templates in thestandard library.
Article Title
Authors
Abstract
Professor Introduction: Investigating Interpersonal Communication
Research in progress for SPCH 1318: Interpersonal Communication
Faculty Mentor: Kerry Loinette, Ph.D.
The following paper represents work produced by a student in an Interpersonal Communication course at Collin College. Students who take interpersonal communication, SPCH 1318, learn about communication in a variety of relationship types including friendship, romantic, familial, and work-place. They are exposed to theories and principles that focus on successful communication behaviors for the creation or initiation of a relationship, the maintenance or care of a relationship, and the termination or ending of a relationship.
In what follows is a student's attempt to understand a very specific interpersonal communication experience. The project addressed how divorced parents perform their co-parenting duties. Once a topic is selected, students are then asked to read existing literature about their topic, create an open-ended survey about their topic, analyze the results of their survey, and write a final paper about their topic.
This paper is the result of the semester long research process. Students are provided with a variety of information including how to format, how to write appropriate open-ended questions, and how to analyze data. Students conduct their projects largely outside of class time. Students are encouraged to select and research topics that interest them and provide insight, be it personal or professional, into interpersonal communication.
Recommended Citation
Farrar, Elizabeth (2017) 'The Parent Trap: Communication About Coparenting Between Divorced Couples,' Quest: Vol. 1 , Article 4.
Available at: https://digitalcommons.collin.edu/quest/vol1/iss1/4
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