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Backport PR #6005: Changed right arrow key movement function to mirror left arrow key...
Backport PR #6005: Changed right arrow key movement function to mirror left arrow key Seems to solve Issue #5926 on this machine, and passing the test file locally. Changed from `cursor.movePosition` to `self._control.moveCursor`, the latter is what the left-arrow key uses. Also removed line 1373 which seems unnecessary and which prevents the cursor from moving at all. I'm not certain how to further test this to make sure nothing was broken.
Brian E. Granger - - Load All Authors

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Background Jobs

We start by loading the backgroundjobs library and defining a few trivial functions to illustrate things with.

In [1]:
from __future__ import print_function
from IPython.lib import backgroundjobs as bg

import sys
import time

def sleepfunc(interval=2, *a, **kw):
    args = dict(interval=interval,
                args=a,
                kwargs=kw)
    time.sleep(interval)
    return args

def diefunc(interval=2, *a, **kw):
    time.sleep(interval)
    raise Exception("Dead job with interval %s" % interval)

def printfunc(interval=1, reps=5):
    for n in range(reps):
        time.sleep(interval)
        print('In the background...', n)
        sys.stdout.flush()
    print('All done!')
    sys.stdout.flush()

Now, we can create a job manager (called simply jobs) and use it to submit new jobs.


Run the cell below and wait a few seconds for the whole thing to finish, until you see the "All done!" printout.
In [2]:
jobs = bg.BackgroundJobManager()

# Start a few jobs, the first one will have ID # 0
jobs.new(sleepfunc, 4)
jobs.new(sleepfunc, kw={'reps':2})
jobs.new('printfunc(1,3)')

# This makes a couple of jobs which will die.  Let's keep a reference to
# them for easier traceback reporting later
diejob1 = jobs.new(diefunc, 1)
diejob2 = jobs.new(diefunc, 2)

Starting job # 0 in a separate thread.
Starting job # 2 in a separate thread.
Starting job # 3 in a separate thread.
Starting job # 4 in a separate thread.
Starting job # 5 in a separate thread.

You can check the status of your jobs at any time:

In [3]:
jobs.status()

In the background... 0
Running jobs:
0 : <function sleepfunc at 0x102cc6848>
2 : <function sleepfunc at 0x102cc6848>
3 : printfunc(1,3)
5 : <function diefunc at 0x102cc68c0>

Dead jobs:
4 : <function diefunc at 0x102cc68c0>

For any completed job, you can get its result easily:

In [4]:
jobs[0].result
j0 = jobs[0]
j0.join?

You can get the traceback of any dead job. Run the line below again interactively until it prints a traceback (check the status of the job):

In [5]:
print "Status of diejob1:", diejob1.status
diejob1.traceback()  # jobs.traceback(4) would also work here, with the job number

In the background... 1
In the background... 2
All done!

  File "<ipython-input-5-a90bd59af669>", line 1
    print "Status of diejob1:", diejob1.status
                             ^
SyntaxError: invalid syntax

This will print all tracebacks for all dead jobs:

In [6]:
jobs.traceback()

Traceback for: <BackgroundJob #4: <function diefunc at 0x102cc68c0>>
---------------------------------------------------------------------------
Exception                                 Traceback (most recent call last)
/Users/bgranger/Documents/Computing/IPython/code/ipython/IPython/lib/backgroundjobs.pyc in call(self)
    489 
    490     def call(self):
--> 491         return self.func(*self.args, **self.kwargs)

<ipython-input-1-7391f8ae281b> in diefunc(interval, *a, **kw)
     14 def diefunc(interval=2, *a, **kw):
     15     time.sleep(interval)
---> 16     raise Exception("Dead job with interval %s" % interval)
     17 
     18 def printfunc(interval=1, reps=5):

Exception: Dead job with interval 1

Traceback for: <BackgroundJob #5: <function diefunc at 0x102cc68c0>>
---------------------------------------------------------------------------
Exception                                 Traceback (most recent call last)
/Users/bgranger/Documents/Computing/IPython/code/ipython/IPython/lib/backgroundjobs.pyc in call(self)
    489 
    490     def call(self):
--> 491         return self.func(*self.args, **self.kwargs)

<ipython-input-1-7391f8ae281b> in diefunc(interval, *a, **kw)
     14 def diefunc(interval=2, *a, **kw):
     15     time.sleep(interval)
---> 16     raise Exception("Dead job with interval %s" % interval)
     17 
     18 def printfunc(interval=1, reps=5):

Exception: Dead job with interval 2

The job manager can be flushed of all completed jobs at any time:

In [7]:
jobs.flush()

Flushing 3 Completed jobs.
Flushing 2 Dead jobs.

After that, the status is simply empty:

In [8]:
jobs.status()

It's easy to wait on a job:

In [9]:
j = jobs.new(sleepfunc, 2)
print("Will wait for j now...")
sys.stdout.flush()
j.join()
print("Result from j:")
j.result

Starting job # 0 in a separate thread.
Will wait for j now...

Result from j:
Out[9]:
{'args': (), 'interval': 2, 'kwargs': {}}