Limitless and
recursion-free
recursion limits!

>>> def factorial(n):
... if n == 1:
... return 1
... else:
... return n * factorial(n - 1)

>>> factorial(10)
3628800

>>> factorial(500)
1220136825991110068701238785423046926253574342803192842192413588385845373153881
9976054964475022032818630136164771482035841633787220781772004807852051593292854
7790757193933060377296085908627042917454788242491272634430567017327076946106280
2310452644218878789465754777149863494367781037644274033827365397471386477878495
4384895955375379904232410612713269843277457155463099772027810145610811883737095
3101635632443298702956389662891165897476957208792692887128178007026517450776841
0719624390394322536422605234945850129918571501248706961568141625359056693423813
0088562492468915641267756544818865065938479517753608940057452389403357984763639
4490531306232374906644504882466507594673586207463792518420045936969298102226397
1952597190945217823331756934581508552332820762820023402626907898342451712006207
7146409794561161276291459512372299133401695523638509428855920187274337951730145
8635757082835578015873543276888868012039988238470215146760544540766353598417443
0480128938313896881639487469658817504506926365338175055478128640000000000000000
0000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000L

>>> factorial(999)
40238726007709377354370243392300398571937486421071463254379991042993851239862902059204420848696940480047998
86101971960586316668729948085589013238296699445909974245040870737599188236277271887325197795059509952761208
74975462497043601418278094646496291056393887437886487337119181045825783647849977012476632889835955735432513
18532395846307555740911426241747434934755342864657661166779739666882029120737914385371958824980812686783837
45597317461360853795345242215865932019280908782973084313928444032812315586110369768013573042161687476096758
71348312025478589320767169132448426236131412508780208000261683151027341827977704784635868170164365024153691
39828126481021309276124489635992870511496497541990934222156683257208082133318611681155361583654698404670897
56029009505376164758477284218896796462449451607653534081989013854424879849599533191017233555566021394503997
36280750137837615307127761926849034352625200015888535147331611702103968175921510907788019393178114194545257
22386554146106289218796022383897147608850627686296714667469756291123408243920816015378088989396451826324367
16167621791689097799119037540312746222899880051954444142820121873617459926429565817466283029555702990243241
53181617210465832036786906117260158783520751516284225540265170483304226143974286933061690897968482590125458
32716822645806652676995865268227280707578139185817888965220816434834482599326604336766017699961283186078838
61502794659551311565520360939881806121385586003014356945272242063446317974605946825731037900840244324384656
57245014402821885252470935190620929023136493273497565513958720559654228749774011413346962715422845862377387
53823048386568897646192738381490014076731044664025989949022222176590433990188601856652648506179970235619389
70178600408118897299183110211712298459016419210688843871218556461249607987229085192968193723886426148396573
82291123125024186649353143970137428531926649875337218940694281434118520158014123344828015051399694290153483
07764456909907315243327828826986460278986432113908350621709500259738986355427719674282224875758676575234422
02075736305694988250879689281627538488633969099598262809561214509948717012445164612603790293091208890869420
28510640182154399457156805941872748998094254742173582401063677404595741785160829230135358081840096996372524
23056085590370062427124341690900415369010593398383577793941097002775347200000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000L

>>> factorial(1000)

File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
RuntimeError: maximum recursion depth exceeded

:(

Recursion limit

>>> import sys
>>> sys.setrecursionlimit(10**8)

>>> factorial(1000)
40238726007709377354370243392300398571937486421071463254379991042993851239862902059204420848696940480047998
86101971960586316668729948085589013238296699445909974245040870737599188236277271887325197795059509952761208
74975462497043601418278094646496291056393887437886487337119181045825783647849977012476632889835955735432513
18532395846307555740911426241747434934755342864657661166779739666882029120737914385371958824980812686783837
45597317461360853795345242215865932019280908782973084313928444032812315586110369768013573042161687476096758
71348312025478589320767169132448426236131412508780208000261683151027341827977704784635868170164365024153691
39828126481021309276124489635992870511496497541990934222156683257208082133318611681155361583654698404670897
56029009505376164758477284218896796462449451607653534081989013854424879849599533191017233555566021394503997
36280750137837615307127761926849034352625200015888535147331611702103968175921510907788019393178114194545257
22386554146106289218796022383897147608850627686296714667469756291123408243920816015378088989396451826324367
16167621791689097799119037540312746222899880051954444142820121873617459926429565817466283029555702990243241
53181617210465832036786906117260158783520751516284225540265170483304226143974286933061690897968482590125458
32716822645806652676995865268227280707578139185817888965220816434834482599326604336766017699961283186078838
61502794659551311565520360939881806121385586003014356945272242063446317974605946825731037900840244324384656
57245014402821885252470935190620929023136493273497565513958720559654228749774011413346962715422845862377387
53823048386568897646192738381490014076731044664025989949022222176590433990188601856652648506179970235619389
70178600408118897299183110211712298459016419210688843871218556461249607987229085192968193723886426148396573
82291123125024186649353143970137428531926649875337218940694281434118520158014123344828015051399694290153483
07764456909907315243327828826986460278986432113908350621709500259738986355427719674282224875758676575234422
02075736305694988250879689281627538488633969099598262809561214509948717012445164612603790293091208890869420
28510640182154399457156805941872748998094254742173582401063677404595741785160829230135358081840096996372524
23056085590370062427124341690900415369010593398383577793941097002775347200000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
L

>>> factorial(1000000)

>>> factorial(1000000)
Segmentation fault: 11

:( :( :(

:D

:D

>>> def factorial(n):
... if n == 1:
... return 1
... else:
... return n * factorial(n - 1)

if (tstate->recursion_depth > recursion_limit) {
--tstate->recursion_depth;
PyErr_Format(PyExc_RuntimeError,
"maximum recursion depth exceeded%s",
where);
return -1;
}

...
c -------------
a | factorial |
l -------------
l | factorial |
-------------
s | factorial |
t -------------
a | factorial |
c -------------
k | REPL | <-- this one counts!
-------------

:D

Tail Call Optimization

c -------------
a | factorial | (1) >>> def factorial(n):
l ------------- ... if n == 1:
l | factorial | (2) ... return 1
------------- ... else:
s | factorial | (3) ... return n * factorial(n - 1)
t -------------
a | factorial | (4)
c -------------
k | factorial | (5)
-------------
| REPL |
-------------

def factorial(n, accumulator):
if n <= 1:
return accumulator
else:
return factorial(n-1, accumulator * n)

>>> factorial(1000)

File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
File "<stdin>", line 5, in factorial
RuntimeError: maximum recursion depth exceeded

OR DOES IT.
with Liuda Nikolaeva and Paul Tagliamonte

def fact(n, accumulator):
10
if n <= 1:
return accumulator
else:
n = n - 1;
accumulator = accumulator * n
GOTO 10
# return fact(n-1, accum*n)

or is there

>>> import dis
>>> dis.dis(factorial)
2 0 LOAD_FAST 0 (n)
3 LOAD_CONST 1 (1)
6 COMPARE_OP 1 (<=)
9 POP_JUMP_IF_FALSE 16
3 12 LOAD_FAST 1 (accumulator)
15 RETURN_VALUE
5 >> 16 LOAD_GLOBAL 0 (factorial)
19 LOAD_FAST 0 (n)
22 LOAD_CONST 1 (1)
25 BINARY_SUBTRACT
26 LOAD_FAST 1 (accumulator)
29 LOAD_FAST 0 (n)
32 BINARY_MULTIPLY
33 CALL_FUNCTION 2
36 RETURN_VALUE
37 LOAD_CONST 0 (None)
40 RETURN_VALUE

>>> import dis
>>> dis.dis(factorial)
2 0 LOAD_FAST 0 (n)
3 LOAD_CONST 1 (1)
6 COMPARE_OP 1 (<=)
9 POP_JUMP_IF_FALSE 16
3 12 LOAD_FAST 1 (accumulator)
15 RETURN_VALUE
5 >> 16 NOP
19 LOAD_FAST 0 (n)
22 LOAD_CONST 1 (1)
25 BINARY_SUBTRACT
26 LOAD_FAST 1 (accumulator)
29 LOAD_FAST 0 (n)
32 BINARY_MULTIPLY
33 JUMP_ABSOLUTE 0
36 RETURN_VALUE
37 LOAD_CONST 0 (None)
40 RETURN_VALUE

>>> def hi():
... print("hi!")
...
>>> def nope():
... print("haha, nope!")
...
>>> hi.__code__ = nope.__code__
>>> hi()
haha, nope!

def tail_recurse(fn):
new_bytecode = []
code_obj = fn.__code__
for byte, arg in consume(code_obj.co_code):
name = opcode.opname[byte]
if name == "LOAD_GLOBAL" and code_obj.co_names[arg] == fn.__name__:
pass
elif name == "CALL_FUNCTION":
for i in range(arg):
new_bytecode.append(opmap["STORE_FAST"])
new_bytecode += split(arg - i - 1)
new_bytecode.append(opmap["JUMP_ABSOLUTE"])
new_bytecode += split(0) # jump to beginning of bytecode
else:
new_bytecode.append(byte)
if arg is not None:
new_bytecode += split(arg)
return "".join([chr(b) for b in new_bytecode])

$ python factorial_tco.py 1000
40238726007709377354370243392300398571937486421071463254379991042993851239862902059204420848696940480047998
86101971960586316668729948085589013238296699445909974245040870737599188236277271887325197795059509952761208
74975462497043601418278094646496291056393887437886487337119181045825783647849977012476632889835955735432513
18532395846307555740911426241747434934755342864657661166779739666882029120737914385371958824980812686783837
45597317461360853795345242215865932019280908782973084313928444032812315586110369768013573042161687476096758
71348312025478589320767169132448426236131412508780208000261683151027341827977704784635868170164365024153691
39828126481021309276124489635992870511496497541990934222156683257208082133318611681155361583654698404670897
56029009505376164758477284218896796462449451607653534081989013854424879849599533191017233555566021394503997
36280750137837615307127761926849034352625200015888535147331611702103968175921510907788019393178114194545257
22386554146106289218796022383897147608850627686296714667469756291123408243920816015378088989396451826324367
16167621791689097799119037540312746222899880051954444142820121873617459926429565817466283029555702990243241
53181617210465832036786906117260158783520751516284225540265170483304226143974286933061690897968482590125458
32716822645806652676995865268227280707578139185817888965220816434834482599326604336766017699961283186078838
61502794659551311565520360939881806121385586003014356945272242063446317974605946825731037900840244324384656
57245014402821885252470935190620929023136493273497565513958720559654228749774011413346962715422845862377387
53823048386568897646192738381490014076731044664025989949022222176590433990188601856652648506179970235619389
70178600408118897299183110211712298459016419210688843871218556461249607987229085192968193723886426148396573
82291123125024186649353143970137428531926649875337218940694281434118520158014123344828015051399694290153483
07764456909907315243327828826986460278986432113908350621709500259738986355427719674282224875758676575234422
02075736305694988250879689281627538488633969099598262809561214509948717012445164612603790293091208890869420
28510640182154399457156805941872748998094254742173582401063677404595741785160829230135358081840096996372524
23056085590370062427124341690900415369010593398383577793941097002775347200000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
L

$ python factorial_tco.py 1000000 # ONE MILLION

:D

>>> sys.setrecursionlimit(1)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
RuntimeError
>>> sys.setrecursionlimit(5)
RuntimeError
>>> sys.setrecursionlimit(10)
RuntimeError
>>> sys.setrecursionlimit(100)
RuntimeError

>>> sys.setrecursionlimit(1)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
RuntimeError
>>> sys.setrecursionlimit(5)
RuntimeError
>>> sys.setrecursionlimit(10)
RuntimeError
>>> sys.setrecursionlimit(100)
RuntimeError
>>> a = 1
RuntimeError
>>> 7
RuntimeError

>>> ^D
Exception RuntimeError: 'maximum recursion depth exceeded'
in <function _remove at 0x103b9e6e0> ignored
Exception RuntimeError: 'maximum recursion depth exceeded'
in <function _remove at 0x103ba25f0> ignored

!! :D