def my_func(aaa):
print aaa     # <---- this will print the VALUE of passed parameter 'aaa' 
# ..... but how to print the NAME of the 'aaa' above as called by a parent function main() - i.e. 

def main():
test_var = 123
my_func(test_var)

def my_func(aaa, main_var):
    mvar = [key for key, val in main_var.items() if val==aaa][0]
    print aaa, main_var, mvar  # 123 {'test_var': 123} test_var
 
def main():
    test_var = 123
    my_func(test_var, vars())
 
main()

def main():
    a = 1
    b = 2
    c = 3
    # local variable dictionary
    main_var = vars()
    print main_var  # {'a': 1, 'c': 3, 'b': 2}
 
    # get the key (variable name) of a certain value, for instance 3
    mvar = [key for key, val in main_var.items() if val==3][0]
    print mvar  # c
 
    # in somewhat longer form ...
    mvar_list = []
    # extract the key:value pairs from the dictionary
    for key, val in main_var.items():
        # if value is 3 save the key in a list
        if val == 3:
            mvar_list.append(key)
    print mvar_list     # ['c']
    # pick the first item on the list
    print mvar_list[0]  # c
 
main()

...

q = [process(x) for x in somelist if condition(x)]

is a shorthand notation for ...
q = []
for x in somelist:
    if condition(x):
        q.append(process(x))

...

def my_func(aaa, main_var=None):
    try:
        mvar = [key for key, val in main_var.items() if val==aaa][0]
        print aaa, main_var, mvar
    except:
        print aaa
    # other code follows
    pass
 
def main():
    test_var = 123
    my_func(test_var, vars())
    my_func(123, vars())
    my_func(456, vars())
    my_func(123)
 
main()
 
"""
my output -->
123 {'test_var': 123} test_var
123 {'test_var': 123} test_var
456
123
"""