Retrieve locals() in order of variable declaration - python

Question

For example,

a = 1

b = 2 

c = 3

When call locals(), I get

{ 'a': 1, 'c': 3, 'b': 2, '__builtins__': <module '__builtin__' (built-in)>, '__package__': None, '__name__': '__main__', '__doc__': None }

How can I retrieve local variables from locals() as the order I defined?

Answer 1

You can do this in a function by accessing the code object.

The __code__ object's .co_varnames attribute stores the variables in the order defined. This expanded example is instructive in that it shows how arguments are passed to the function, as well as internally defined variables:

def foo(a, b, c=3, d=4, *args, **kwargs):
    e = 5
    f = 6
    g = 7
    for var in foo.__code__.co_varnames:
        print(var, locals()[var])

and now (will look slightly different in Python 2 due to difference between print statement and function.):

>>> foo(1, 2, *(11, 12, 13), **{'h': 14, 'i': 15, 'j': 16})
a 1
b 2
c 11
d 12
args (13,)
kwargs {'i': 15, 'h': 14, 'j': 16}
e 5
f 6
g 7
var var

Answer 2

In light of the fact that locals() doesn't retrieve function parameters in order, I created a utility function for debugging purposes.

import inspect
import logging
import traceback

def get_function_name():
    return traceback.extract_stack(None, 2)[0][2]

def get_function_parameters_and_values():
    frame = inspect.currentframe().f_back
    args, _, _, values = inspect.getargvalues(frame)
    return ([(i, values[i]) for i in args])

def my_func(a, b, c=None):
    logging.info('Running ' + get_function_name() + '(' + str(get_function_parameters_and_values()) +')')
    pass

logger = logging.getLogger()
handler = logging.StreamHandler()
formatter = logging.Formatter(
    '%(asctime)s [%(levelname)s] -> %(message)s')
handler.setFormatter(formatter)
logger.addHandler(handler)
logger.setLevel(logging.INFO)

my_func(1, 3) # 2016-03-25 17:16:06,927 [INFO] -> Running my_func([('a', 1), ('b', 3), ('c', None)])