Python code object, function, and default parameters

Investigation

I have this program

def gen_baz():
    return 2

def gen_bar(a, b, c=1):
    return a, b, c

# ---------- #

# Save the code objects
c1 = gen_bar.__code__
c2 = gen_baz.__code__

dis.dis(gen_bar) # [Disassambly 1]
print(inspect.getsource(gen_bar)) # [Inspect 1]

bar = gen_bar(1, 2) # bar: (1, 2, 1)
baz = gen_baz() # baz: 2
print(f"before: bar={bar}, baz={baz}")

# --------- #

gen_bar.__code__, gen_baz.__code__ = c2, c1 # swap code objects between 2 functions

dis.dis(gen_baz) # [Disassambly 2]
print(inspect.getsource(gen_baz))  # [Inspect 1]

bar = gen_bar() # bar: 2
baz = gen_baz(1, 2) # baz: [Error 1]
print(f"after: bar={bar}, baz={baz}")

Here are the outputs with Disassembly and Inspect

[Disassembly 1 & 2]
 17           0 LOAD_FAST                0 (a)
              2 LOAD_FAST                1 (b)
              4 LOAD_FAST                2 (c)
              6 BUILD_TUPLE              3
              8 RETURN_VALUE

[Inspect 1 & 2]
def gen_bar(a, b, c=1):
    return a, b, c

[Error 1]
Traceback (most recent call last):
  File "C:\Users\something\test.py", line 32, in <module>
    baz = gen_baz(1, 2)
TypeError: gen_baz() missing 1 required positional argument: 'c'

Question

1. Why after I swapped the code objects between baz and bar, the program crashed? Even though they have identical byte code and inspect result
2. Where is the default parameter in python stored? Does it come along with the function object but not the code object? If so, then how does Inspect module gives me c=1 on the second inspection?

Thanks a lot!

>Solution :

Check the docs:

• __code__: code object containing compiled function bytecode
• __defaults__: tuple of any default values for positional or keyword parameters
• __kwdefaults__: mapping of any default values for keyword-only parameters