I want to write a function which imports modules the first time, and reloads
them afterwards, but I am running into problems with global variables and exec.
I will include a full script, but let me elaborate first.
Essentially what you need is
def import_or_reload():
"""assume we want to load or reload sys"""
if 'sys' in dir():
reload(sys)
else:
import sys
but this runs into the problem that sys is imported within the local scope of
the function, so you insert a global statement
def import_or_reload2():
"""Add 'global sys'"""
global sys
if 'sys' in dir():
reload(sys)
else:
import sys
'sys' is still not in dir() as dir() pertains to the local scope of the
function, but one can get around this by creating a local modules list and
adding the imported modules to it
def import_or_reload3():
"""Add 'global modules'"""
global sys
global modules
if 'sys' in modules:
reload(sys)
else:
import sys
modules.append('sys')
now lets add a parameter to the function signature, so any module name can be
passed as an argument and loaded
def import_or_reload4(module_name):
"""Add exec"""
exec 'global %s'%module_name
global modules
if module_name in modules:
exec 'reload(%s)'%module_name
else:
exec 'import %s'%module_name
exec 'modules.append(\'%s\')'%module_name
but this doesn't work as global does not cooperate with exec
is there a __reload__('X') function like there is an __import__(‘X’) function?
Also is there a better way to import modules at run time?
Cheers and here is the test script in case you can't access the attachment
def a():
global modules
global sys
import sys
modules.append('sys')
def b():
global modules
global sys
reload(sys)
def c(module_name):
global modules
exec 'global %s'%module_name
exec 'import %s'%module_name
modules.append(module_name)
def test():
global modules
global sys
#create the module list to contain all the modules
modules=[]
print 'originally dir() returns:'
print dir()
a()
print 'function a() properly imports the following module:'
print sys
print 'is %s in %s->%s'%('sys',modules,'sys' in modules)
b()
print 'function b() properly reloads the following module:'
print sys
print 'is %s still in %s->%s'%('sys',modules,'sys' in modules)
try:
c('os')
print 'function c() properly imports the following module:'
except:
print 'function c() failed to import module os'
print 'is %s in %s->%s'%('os',modules,'os' in modules)
try:
print os
print 'is %s still in %s->%s'%('os',modules,'os' in modules)
except:
print 'os was loaded, but is not visible outside of the scope of c()'
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def a():
global modules
global sys
import sys
modules.append('sys')
def b():
global modules
global sys
reload(sys)
def c(module_name):
global modules
exec 'global %s'%module_name
exec 'import %s'%module_name
modules.append(module_name)
def test():
global modules
global sys
#create the module list to contain all the modules
modules=[]
print 'originally dir() returns:'
print dir()
a()
print 'function a() properly imports the following module:'
print sys
print 'is %s in %s->%s'%('sys',modules,'sys' in modules)
b()
print 'function b() properly reloads the following module:'
print sys
print 'is %s still in %s->%s'%('sys',modules,'sys' in modules)
try:
c('os')
print 'function c() properly imports the following module:'
except:
print 'function c() failed to import module os'
print 'is %s in %s->%s'%('os',modules,'os' in modules)
try:
print os
print 'is %s still in %s->%s'%('os',modules,'os' in modules)
except:
print 'os was loaded, but is not visible outside of the scope of c()'
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