What is a "code object" mentioned in this TypeError message?
Question:
While trying to use Python’s exec statement, I got the following error:
TypeError: exec: arg 1 must be a string, file, or code object
I don’t want to pass in a string or a file, but what is a code object, and how do I create one?
Answers:
One way to create a code object is to use compile built-in function:
>>> compile('sum([1, 2, 3])', '', 'single')
<code object <module> at 0x19ad730, file "", line 1>
>>> exec compile('sum([1, 2, 3])', '', 'single')
6
>>> compile('print "Hello world"', '', 'exec')
<code object <module> at 0x19add30, file "", line 1>
>>> exec compile('print "Hello world"', '', 'exec')
Hello world
also, functions have the function attribute __code__ (also known as func_code in older versions) from which you can obtain the function’s code object:
>>> def f(s): print s
...
>>> f.__code__
<code object f at 0x19aa1b0, file "<stdin>", line 1>
Code objects are described here:
Code objects represent byte-compiled
executable Python code, or bytecode.
The difference between a code object
and a function object is that the
function object contains an explicit
reference to the function’s globals
(the module in which it was defined),
while a code object contains no
context; also the default argument
values are stored in the function
object, not in the code object
(because they represent values
calculated at run-time). Unlike
function objects, code objects are
immutable and contain no references
(directly or indirectly) to mutable
objects.
There is an excellent blog post by Dan Crosta explaining this topic, including how to create code objects manually, and how to disassemble them again:
While trying to use Python’s exec statement, I got the following error:
TypeError: exec: arg 1 must be a string, file, or code object
I don’t want to pass in a string or a file, but what is a code object, and how do I create one?
One way to create a code object is to use compile built-in function:
>>> compile('sum([1, 2, 3])', '', 'single')
<code object <module> at 0x19ad730, file "", line 1>
>>> exec compile('sum([1, 2, 3])', '', 'single')
6
>>> compile('print "Hello world"', '', 'exec')
<code object <module> at 0x19add30, file "", line 1>
>>> exec compile('print "Hello world"', '', 'exec')
Hello world
also, functions have the function attribute __code__ (also known as func_code in older versions) from which you can obtain the function’s code object:
>>> def f(s): print s
...
>>> f.__code__
<code object f at 0x19aa1b0, file "<stdin>", line 1>
Code objects are described here:
Code objects represent byte-compiled
executable Python code, or bytecode.
The difference between a code object
and a function object is that the
function object contains an explicit
reference to the function’s globals
(the module in which it was defined),
while a code object contains no
context; also the default argument
values are stored in the function
object, not in the code object
(because they represent values
calculated at run-time). Unlike
function objects, code objects are
immutable and contain no references
(directly or indirectly) to mutable
objects.
There is an excellent blog post by Dan Crosta explaining this topic, including how to create code objects manually, and how to disassemble them again: