docs/examples/core/example-embed.py

#!/usr/bin/env python

"""An example of how to embed an IPython shell into a running program.

Please see the documentation in the IPython.Shell module for more details.

The accompanying file example-embed-short.py has quick code fragments for
embedding which you can cut and paste in your code once you understand how
things work.

The code in this file is deliberately extra-verbose, meant for learning."""

# The basics to get you going:

# IPython sets the __IPYTHON__ variable so you can know if you have nested
# copies running.

# Try running this code both at the command line and from inside IPython (with
# %run example-embed.py)
try:
    __IPYTHON__
except NameError:
    nested = 0
    args = ['']
else:
    print "Running nested copies of IPython."
    print "The prompts for the nested copy have been modified"
    nested = 1
    # what the embedded instance will see as sys.argv:
    args = ['-pi1','In <\\#>: ','-pi2','   .\\D.: ',
            '-po','Out<\\#>: ','-nosep']

# First import the embeddable shell class
from IPython.core.shell import IPShellEmbed

# Now create an instance of the embeddable shell. The first argument is a
# string with options exactly as you would type them if you were starting
# IPython at the system command line. Any parameters you want to define for
# configuration can thus be specified here.
ipshell = IPShellEmbed(args,
                       banner = 'Dropping into IPython',
                       exit_msg = 'Leaving Interpreter, back to program.')

# Make a second instance, you can have as many as you want.
if nested:
    args[1] = 'In2<\\#>'
else:
    args = ['-pi1','In2<\\#>: ','-pi2','   .\\D.: ',
            '-po','Out<\\#>: ','-nosep']
ipshell2 = IPShellEmbed(args,banner = 'Second IPython instance.')

print '\nHello. This is printed from the main controller program.\n'

# You can then call ipshell() anywhere you need it (with an optional
# message):
ipshell('***Called from top level. '
        'Hit Ctrl-D to exit interpreter and continue program.\n'
        'Note that if you use %kill_embedded, you can fully deactivate\n'
        'This embedded instance so it will never turn on again')

print '\nBack in caller program, moving along...\n'

#---------------------------------------------------------------------------
# More details:

# IPShellEmbed instances don't print the standard system banner and
# messages. The IPython banner (which actually may contain initialization
# messages) is available as <instance>.IP.BANNER in case you want it.

# IPShellEmbed instances print the following information everytime they
# start:

# - A global startup banner.

# - A call-specific header string, which you can use to indicate where in the
# execution flow the shell is starting.

# They also print an exit message every time they exit.

# Both the startup banner and the exit message default to None, and can be set
# either at the instance constructor or at any other time with the
# set_banner() and set_exit_msg() methods.

# The shell instance can be also put in 'dummy' mode globally or on a per-call
# basis. This gives you fine control for debugging without having to change
# code all over the place.

# The code below illustrates all this.


# This is how the global banner and exit_msg can be reset at any point
ipshell.set_banner('Entering interpreter - New Banner')
ipshell.set_exit_msg('Leaving interpreter - New exit_msg')

def foo(m):
    s = 'spam'
    ipshell('***In foo(). Try @whos, or print s or m:')
    print 'foo says m = ',m

def bar(n):
    s = 'eggs'
    ipshell('***In bar(). Try @whos, or print s or n:')
    print 'bar says n = ',n
    
# Some calls to the above functions which will trigger IPython:
print 'Main program calling foo("eggs")\n'
foo('eggs')

# The shell can be put in 'dummy' mode where calls to it silently return. This
# allows you, for example, to globally turn off debugging for a program with a
# single call.
ipshell.set_dummy_mode(1)
print '\nTrying to call IPython which is now "dummy":'
ipshell()
print 'Nothing happened...'
# The global 'dummy' mode can still be overridden for a single call
print '\nOverriding dummy mode manually:'
ipshell(dummy=0)

# Reactivate the IPython shell
ipshell.set_dummy_mode(0)

print 'You can even have multiple embedded instances:'
ipshell2()

print '\nMain program calling bar("spam")\n'
bar('spam')

print 'Main program finished. Bye!'

#********************** End of file <example-embed.py> ***********************