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Architecture of CPython
the Bricks !
PART 1
by Stephane Wirtel
PyCon.Canada 2016 - Toronto - 11/13/2016
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I am ... Stephane
CPython contributor
blah blah Python blah
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Agenda
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Agenda
What is the Bytecode ?
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Agenda
What is the Bytecode ?
Code -> Bytecode
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Agenda
What is the Bytecode ?
Code -> Bytecode
Bytecode
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Agenda
What is the Bytecode ?
Code -> Bytecode
Bytecode
.pyc file
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Agenda
What is the Bytecode ?
Code -> Bytecode
Bytecode
.pyc file
Virtual Machine
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Bytecode
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Bytecode
Instructions to follow
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Bytecode
Instructions to follow
Used by "Virtual" Machine
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Example of Bytecode
In a restaurant... I am the "Virtual" Machine...
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Example of Bytecode
In a restaurant... I am the "Virtual" Machine...
SAY "Hello""
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Example of Bytecode
In a restaurant... I am the "Virtual" Machine...
SAY "Hello""
SET CMD "Fish and Chips"
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Example of Bytecode
In a restaurant... I am the "Virtual" Machine...
SAY "Hello""
SET CMD "Fish and Chips"
ORDER CMD
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Example of Bytecode
In a restaurant... I am the "Virtual" Machine...
SAY "Hello""
SET CMD "Fish and Chips"
ORDER CMD
PREPARE "Money"
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Example of Bytecode
In a restaurant... I am the "Virtual" Machine...
SAY "Hello""
SET CMD "Fish and Chips"
ORDER CMD
PREPARE "Money"
WAIT_MINUTES 5
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Example of Bytecode
In a restaurant... I am the "Virtual" Machine...
SAY "Hello""
SET CMD "Fish and Chips"
ORDER CMD
PREPARE "Money"
WAIT_MINUTES 5
RECEIVE CMD
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Example of Bytecode
In a restaurant... I am the "Virtual" Machine...
SAY "Hello""
SET CMD "Fish and Chips"
ORDER CMD
PREPARE "Money"
WAIT_MINUTES 5
RECEIVE CMD
EAT CMD
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Example of Bytecode
In a restaurant... I am the "Virtual" Machine...
SAY "Hello""
SET CMD "Fish and Chips"
ORDER CMD
PREPARE "Money"
WAIT_MINUTES 5
RECEIVE CMD
EAT CMD
PAY "Restaurant"
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Code -> Bytecode
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The Bricks!
Developer
Code
Lexer/Parser AST
Compiler Peepholer/Optimizer
ByteCode Reader Inter pr eter
Parsing
Compiler
VirtualMachine
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Code > Lexer > Parser > AST > Compiler
>>> expr = 'x = 2 + 2'
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Code > Lexer > Parser > AST > Compiler
>>> expr = 'x = 2 + 2'
Lexer
>>> import tokenize
>>> strIO = io.StringIO(expr).readline
>>> tokens = tokenize.generate_tokens(strIO)
>>> pp(list(tokens))
[
TokenInfo(type=NAME, string='x'),
TokenInfo(type=OP, string='='),
TokenInfo(type=NUMBER, string='2'),
TokenInfo(type=OP, string='+'),
TokenInfo(type=NUMBER, string='2'),
TokenInfo(type=ENDMARKER, string=''),
]
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Code > Lexer > Parser > AST > Compiler
>>> expr = 'x = 2 + 2'
Parser and AST
>>> import ast
>>> tree = ast.parse(expr)
>>> ast.dump(tree)
Module(
body=[
Assign(
targets=[Name(id='x')],
value=BinOp(
left=Num(n=2),
op=Add(),
right=Num(n=2)
)
)
]
)
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Code > Lexer > Parser > AST > Compiler
>>> expr = 'x = 2 + 2'
Compiler
>>> import dis
>>> dis.dis(expr)
1 0 LOAD_CONST 2 (4)
3 STORE_NAME 0 (x)
6 LOAD_CONST 1 (None)
9 RETURN_VALUE
Design of the CPython Compiler PEP-0339
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Structure of a .pyc file
Here is the source code
print("Hello")
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Structure of a .pyc file
Here is the source code
print("Hello")
will generate this bytecode
1 0 LOAD_NAME 0 (print)
3 LOAD_CONST 0 ('Hello')
6 CALL_FUNCTION 1 (1 positional, 0 keyword pair)
9 POP_TOP
10 LOAD_CONST 1 (None)
13 RETURN_VALUE
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Structure of a .pyc file
And here is the dump of the binary file
00 160d0d0a 1b911558 0f000000 e3000000 |.......X........|
10 00000001 00000000 00020000 00400000 |.............@..|
20 00730e00 00006500 00640000 83010001 |.s....e..d......|
30 64010053 29025a05 48656c6c 6f4e2901 |d..S).Z.HelloN).|
40 da057072 696e74a9 00720200 00007202 |..print..r....r.|
50 000000fa 0764656d 6f2e7079 da083c6d |.....demo.py......s....|
6f
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Structure of a .pyc file
demo.pyc (Python 3.5)
[Code]
File Name: demo.py
Object Name:
Arg Count: 0
KW Only Arg Count: 0
Locals: 0
Stack Size: 2
Flags: 0x00000040 (CO_NOFREE)
[Names]
'print'
[Var Names]
[Free Vars]
[Cell Vars]
[Constants]
'Hello'
None
[Disassembly]
0 LOAD_NAME 0: print
3 LOAD_CONST 0: 'Hello'
6 CALL_FUNCTION 1
9 POP_TOP
10 LOAD_CONST 1: None
13 RETURN_VALUE
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Structure of a .pyc file
0 6 12
Magic Number Time Stamp Header Size
M ar shalling. . .
M ar shalling. . .
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Structure of a .pyc file
00 160d0d0a 1b911558 0f000000 e3000000 |.......X........|
10 00000001 00000000 00020000 00400000 |.............@..|
20 00730e00 00006500 00640000 83010001 |.s....e..d......|
30 64010053 29025a05 48656c6c 6f4e2901 |d..S).Z.HelloN).|
40 da057072 696e74a9 00720200 00007202 |..print..r....r.|
50 000000fa 0764656d 6f2e7079 da083c6d |.....demo.py......s....|
6f
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Structure of a .pyc file
00 160d0d0a 1b911558 0f000000 e3000000 |.......X........|
10 00000001 00000000 00020000 00400000 |.............@..|
20 00730e00 00006500 00640000 83010001 |.s....e..d......|
30 64010053 29025a05 48656c6c 6f4e2901 |d..S).Z.HelloN).|
40 da057072 696e74a9 00720200 00007202 |..print..r....r.|
50 000000fa 0764656d 6f2e7079 da083c6d |.....demo.py......s....|
6f
0x160D0D0A -> Magic Number
0x1B911558 -> Time Stamp
0x0F000000 -> Header Size
Marshalling in Blue is the code and the variables
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Structure of a .pyc file
Magic Number
0x160D0D0A is based on the version of Python
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Structure of a .pyc file
Magic Number
0x160D0D0A is based on the version of Python
# Python 2.7a0 62211 (introduce MAP_ADD and SET_ADD)
# Python 3.0a5: 3131 (lexical exception stacking, including POP_EXCEPT)
# Python 3.1a0: 3151 (optimize conditional branches:
# Python 3.2a2 3180 (add DELETE_DEREF)
# Python 3.3a4 3230 (revert changes to implicit __class__ closure)
# Python 3.4rc2 3310 (alter __qualname__ computation)
# Python 3.5b2 3350 (add GET_YIELD_FROM_ITER opcode #24400)
# Python 3.5.2 3351 (fix BUILD_MAP_UNPACK_WITH_CALL opcode #27286)
# Python 3.6b2 3378 (add BUILD_TUPLE_UNPACK_WITH_CALL #28257)
See Imp/importlib/_bootstrap_external.py
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Structure of a .pyc file
Magic Number
0x160D0D0A is based on the version of Python
# Python 2.7a0 62211 (introduce MAP_ADD and SET_ADD)
# Python 3.0a5: 3131 (lexical exception stacking, including POP_EXCEPT)
# Python 3.1a0: 3151 (optimize conditional branches:
# Python 3.2a2 3180 (add DELETE_DEREF)
# Python 3.3a4 3230 (revert changes to implicit __class__ closure)
# Python 3.4rc2 3310 (alter __qualname__ computation)
# Python 3.5b2 3350 (add GET_YIELD_FROM_ITER opcode #24400)
# Python 3.5.2 3351 (fix BUILD_MAP_UNPACK_WITH_CALL opcode #27286)
# Python 3.6b2 3378 (add BUILD_TUPLE_UNPACK_WITH_CALL #28257)
>>> import binascii
>>> version = (3350).to_bytes(2, 'little') + b'\r\n'
>>> binascii.hexlify(version)
b'160d0d0a'
See Imp/importlib/_bootstrap_external.py
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Structure of a .pyc file
Time Stamp
0x1B911558 -> Time Stamp, Unix modification
>>> b = bytearray.fromhex('1B911558')
>>> s = struct.unpack('=L', b)
>>> time.asctime(time.localtime(s[0]))
'Sun Oct 30 07:20:11 2016'
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Structure of a .pyc file
Marshalling
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Structure of a .pyc file
Marshalling
Specific format to Python
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Structure of a .pyc file
Marshalling
Specific format to Python
Contains Python Objects (tuple, list, dict, set, number, string, ...)
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Structure of a .pyc file
Marshalling
Specific format to Python
Contains Python Objects (tuple, list, dict, set, number, string, ...)
For each kind of object, there is 1 byte for the type
#define TYPE_NULL '0'
#define TYPE_NONE 'N'
#define TYPE_FALSE 'F'
#define TYPE_TRUE 'T'
...
#define TYPE_INT 'i'
#define TYPE_FLOAT 'f'
#define TYPE_STRING 's'
#define TYPE_TUPLE '('
#define TYPE_LIST '['
#define TYPE_CODE 'c'
...
#define TYPE_ASCII 'a'
#define TYPE_SHORT_ASCII 'z'
...
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Structure of a .pyc file
Marshalling - TYPE_CODE - 'c'
#define TYPE_CODE 'c'
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Ty p
e
ArgCount KwOnly ArgCount NumLocals StackSize Flags
Size/Code (by tes) Consts (tuple) Names (tuple) VarNames (tuple)
FreeVars (tuple) C ellVars (t uple) FileName (by tes) Name (by tes)
Table
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Structure of a .pyc file
Marshalling - TYPE_CODE - 'c'
00 160d0d0a 1b911558 0f000000 e3000000
10 00000001 00000000 00020000 00400000
20 00730e00 00006500 00640000 83010001
30 64010053 29025a05 48656c6c 6f4e2901
40 da057072 696e74a9 00720200 00007202
50 000000fa 0764656d 6f2e7079 da083c6d
60 6f64756c 653e0100 00007300 000000
6f
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Structure of a .pyc file
Marshalling - TYPE_TUPLE - '('
#define TYPE_TUPLE '('
0 8 16
Typ
e
S i ze (byte) Ob je c ts (Tup le , S tri ng , ...)
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Structure of a .pyc file
Marshalling - TYPE_STRING - 's'
#define TYPE_STRING 's'
0 8 16
Typ
e
S i ze (i nt32)
Content (bytes)
Content (bytes)
Content (bytes)
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Structure of a .pyc file
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Structure of a .pyc file
Header
3.5.0
2016-11-09T11:31:0815
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Structure of a .pyc file
Body
0
00
2
64
b'e\x00\x00d\x00\x00\x83\x01\x00\x01d\x01\x00S'
[101, 0, 0, 100, 0, 0, 131, 1, 0, 1, 100, 1, 0, 83]
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Dumpyc
Started a new project (https://github.com/matrixise/dumpyc) (Yesterday)
Only compatible with the bytecode of print('Hello') in Python 3.5
NEED Contributions if you want to help me
TODO list:
Compatible with Python 2.7, 3.3, 3.4, 3.6 and futures versions
Generate a XML, JSON, Dict
Library with Clean API
GUI (TK ?)
github.com/matrixise/dumpyc
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Virtual Machine
A Python Interpreter in 500 lines of code
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Virtual Machine
Requirements ;-)
Stack
Frame
Call Stack
Bytecode
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Virtual Machine
Stack
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Virtual Machine
Stack
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Virtual Machine
Frame
Collection of information and context for a chunk of code
Created and destroyed on the fly
Corresponding to each call of a function
Has a code object
Include/frameobject.h
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Virtual Machine
Call Stack
>>> def bar(y):
... z = y + 3 # <--- (3) ... and the interpreter is here.
... return z
...
>>> def foo():
... a = 1
... b = 2
... return a + bar(b) # <--- (2) ... which is returning a call to bar ...
...
>>> foo() # <--- (1) We're in the middle of a call to foo ...
3
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Virtual Machine
Call Stack
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Bytecode
Instructions to follow
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Bytecode
Instructions to follow
Intermediate Representation of your Code
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Bytecode
Instructions to follow
Intermediate Representation of your Code
Used by "Virtual" Machine
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Bytecode
Instructions to follow
Intermediate Representation of your Code
Used by "Virtual" Machine
Compact Code coded one "BYTE"
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Bytecode
Instructions to follow
Intermediate Representation of your Code
Used by "Virtual" Machine
Compact Code coded one "BYTE"
in 3.6, on 2 BYTES
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Bytecode
Instructions to follow
Intermediate Representation of your Code
Used by "Virtual" Machine
Compact Code coded one "BYTE"
in 3.6, on 2 BYTES
#define POP_TOP 1
#define BINARY_ADD 23
#define RETURN_VALUE 83
#define HAVE_ARGUMENT 90
#define STORE_NAME 90
#define LOAD_CONST 100
#define LOAD_NAME 101
#define CALL_FUNCTION 131
#define HAS_ARG(op) ((op) >= HAVE_ARGUMENT)
See in Include/opcode.h
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Bytecode
>>> x = 'Hello'
>>> y = 'World'
>>> print(x + ' ' + y)
1 0 LOAD_CONST 0 ('Hello')
3 STORE_NAME 0 (x)
2 6 LOAD_CONST 1 ('World')
9 STORE_NAME 1 (y)
3 12 LOAD_NAME 2 (print)
15 LOAD_NAME 0 (x)
18 LOAD_CONST 2 (' ')
21 BINARY_ADD
22 LOAD_NAME 1 (y)
25 BINARY_ADD
26 CALL_FUNCTION 1 (1 positional, 0 keyword pair)
29 POP_TOP
30 LOAD_CONST 3 (None)
33 RETURN_VALUE
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Inside the evaluator
We have the following instructions:
LOAD_CONST
STORE_NAME
LOAD_NAME
BINARY_ADD
CALL_FUNCTION
POP_TOP
RETURN_VALUE
Read Python Bytecode Instructions
TOS = Top of Stack
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LOAD_CONST
1 0 LOAD_CONST 0 ('Hello')
3 STORE_NAME 0 (x)
LOAD_CONST(consti) : Pushes co_consts[consti] onto the stack.
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LOAD_CONST
1 0 LOAD_CONST 0 ('Hello')
3 STORE_NAME 0 (x)
LOAD_CONST(consti) : Pushes co_consts[consti] onto the stack.
TARGET(LOAD_CONST) {
PyObject *value = GETITEM(consts, oparg);
Py_INCREF(value);
PUSH(value);
FAST_DISPATCH();
}
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STORE_NAME
2 6 LOAD_CONST 1 ('World')
9 STORE_NAME 1 (y)
STORE_NAME(namei) : Implements name=TOS.namei is the index of the name in the
attribute co_names of the code object.
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STORE_NAME
2 6 LOAD_CONST 1 ('World')
9 STORE_NAME 1 (y)
STORE_NAME(namei) : Implements name=TOS.namei is the index of the name in the
attribute co_names of the code object.
TARGET(STORE_NAME) {
PyObject *name = GETITEM(names, oparg);
PyObject *v = POP();
PyObject *ns = f->f_locals;
int err;
if (ns == NULL) {
PyErr_Format(PyExc_SystemError,
"no locals found when storing %R", name);
Py_DECREF(v);
goto error;
}
if (PyDict_CheckExact(ns))
err = PyDict_SetItem(ns, name, v);
else
err = PyObject_SetItem(ns, name, v);
Py_DECREF(v);
if (err != 0)
goto error;
DISPATCH();
}
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LOAD_NAME
2 6 LOAD_CONST 1 ('World')
9 STORE_NAME 1 (y)
3 12 LOAD_NAME 2 (print)
15 LOAD_NAME 0 (x)
18 LOAD_CONST 2 (' ')
21 BINARY_ADD
LOAD_NAME(namei) : Pushes the value associated with co_names[namei] on the
stack
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LOAD_NAME
2 6 LOAD_CONST 1 ('World')
9 STORE_NAME 1 (y)
3 12 LOAD_NAME 2 (print)
15 LOAD_NAME 0 (x)
18 LOAD_CONST 2 (' ')
21 BINARY_ADD
LOAD_NAME(namei) : Pushes the value associated with co_names[namei] on the
stack
TARGET(LOAD_NAME) {
PyObject *name = GETITEM(names, oparg);
PyObject *locals = f->f_locals;
PyObject *v;
if (locals == NULL) {
PyErr_Format(PyExc_SystemError,
"no locals when loading %R", name);
goto error;
}
if (PyDict_CheckExact(locals)) {
v = PyDict_GetItem(locals, name);
Py_XINCREF(v);
}
else {
v = PyObject_GetItem(locals, name);
... // if error -> goto error label
}
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BINARY_ADD
3 12 LOAD_NAME 2 (print)
15 LOAD_NAME 0 (x)
18 LOAD_CONST 2 (' ')
21 BINARY_ADD
22 LOAD_NAME 1 (y)
25 BINARY_ADD
BINARY_ADD : Implements TOS = TOS1 + TOS
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BINARY_ADD
3 12 LOAD_NAME 2 (print)
15 LOAD_NAME 0 (x)
18 LOAD_CONST 2 (' ')
21 BINARY_ADD
22 LOAD_NAME 1 (y)
25 BINARY_ADD
BINARY_ADD : Implements TOS = TOS1 + TOS
TARGET(BINARY_ADD) {
PyObject *right = POP();
PyObject *left = TOP();
PyObject *sum;
if (PyUnicode_CheckExact(left) && PyUnicode_CheckExact(right)) {
sum = unicode_concatenate(left, right, f, next_instr);
}
else {
sum = PyNumber_Add(left, right);
Py_DECREF(left);
}
Py_DECREF(right);
SET_TOP(sum);
...
}
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CALL_FUNCTION
22 LOAD_NAME 1 (y)
25 BINARY_ADD
26 CALL_FUNCTION 1 (1 positional, 0 keyword pair)
29 POP_TOP
CALL_FUNCTION(argc) : Call a function.
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CALL_FUNCTION
22 LOAD_NAME 1 (y)
25 BINARY_ADD
26 CALL_FUNCTION 1 (1 positional, 0 keyword pair)
29 POP_TOP
CALL_FUNCTION(argc) : Call a function.
TARGET(CALL_FUNCTION) {
PyObject **sp, *res;
PCALL(PCALL_ALL);
sp = stack_pointer;
res = call_function(&sp, oparg, NULL);
stack_pointer = sp;
PUSH(res);
if (res == NULL) {
goto error;
}
DISPATCH();
}
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POP
_TOP
22 LOAD_NAME 1 (y)
25 BINARY_ADD
26 CALL_FUNCTION 1 (1 positional, 0 keyword pair)
29 POP_TOP
POP_TOP: Remove the top-of-stack item.
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POP
_TOP
22 LOAD_NAME 1 (y)
25 BINARY_ADD
26 CALL_FUNCTION 1 (1 positional, 0 keyword pair)
29 POP_TOP
POP_TOP: Remove the top-of-stack item.
TARGET(POP_TOP) {
PyObject *value = POP();
Py_DECREF(value);
FAST_DISPATCH();
}
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RETURN_VALUE
29 POP_TOP
30 LOAD_CONST 3 (None)
33 RETURN_VALUE
RETURN_VALUE: Returns the TOS to the caller of the function
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RETURN_VALUE
29 POP_TOP
30 LOAD_CONST 3 (None)
33 RETURN_VALUE
RETURN_VALUE: Returns the TOS to the caller of the function
TARGET(RETURN_VALUE) {
retval = POP();
why = WHY_RETURN;
goto fast_block_end;
}
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RETURN_VALUE
29 POP_TOP
30 LOAD_CONST 3 (None)
33 RETURN_VALUE
RETURN_VALUE: Returns the TOS to the caller of the function
TARGET(RETURN_VALUE) {
retval = POP();
why = WHY_RETURN;
goto fast_block_end;
}
why can be:
enum why_code {
WHY_NOT = 0x0001, /* No error */
WHY_EXCEPTION = 0x0002, /* Exception occurred */
WHY_RETURN = 0x0008, /* 'return' statement */
WHY_BREAK = 0x0010, /* 'break' statement */
WHY_CONTINUE = 0x0020, /* 'continue' statement */
WHY_YIELD = 0x0040, /* 'yield' operator */
WHY_SILENCED = 0x0080 /* Exception silenced by 'with' */
};
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Read Python/ceval.c
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Python/ceval.c
792 PyObject *
793 _PyEval_EvalFrameDefault(PyFrameObject *f, int throwflag)
794 {
...
1824 #ifdef CASE_TOO_BIG
1825 default: switch (opcode) {
1826 #endif
...
3693 }
Link to the code of ceval.c
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Python/ceval.c
792 PyObject *
793 _PyEval_EvalFrameDefault(PyFrameObject *f, int throwflag)
794 {
...
1824 #ifdef CASE_TOO_BIG
1825 default: switch (opcode) {
1826 #endif
...
3693 }
Link to the code of ceval.c
2900 lines of CODE
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Welcome to the CPython World ;-)
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Just For Fun
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__ltrace__ feature
Python 3.7.0a0 (default:897fe8fa14b5+, Oct 15 2016, 09:56:54)
>>> __ltrace__ = 'an object'
>>> def foo(bar): return bar + 1
...
0: LOAD_CONST, 0
2: LOAD_CONST, 1
4: MAKE_FUNCTION, 0
6: STORE_NAME, 0
8: LOAD_CONST, 2
10: RETURN_VALUE
>>> print(foo(2))
0: LOAD_NAME, 0
2: LOAD_NAME, 1
4: LOAD_CONST, 0
6: CALL_FUNCTION, 1
0: LOAD_FAST, 0
2: LOAD_CONST, 1
4: BINARY_ADD
6: RETURN_VALUE
8: CALL_FUNCTION, 1
3
10: PRINT_EXPR
12: LOAD_CONST, 1
14: RETURN_VALUE
>>>
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frenchify Python
depuis os importe path
depuis pprint importe pprint comme pp
pour i dans range(5):
print(i)
si i < 3: print("i < 3")
ssi i < 7: print("i < 7")
classe Utilisateur:
déf __init__(moimeme, nom, courriel):
moimeme.nom = nom
moimeme.courriel = courriel
utilisateur = Utilisateur('stephane', '[email protected]')
print("nom : ", utilisateur.nom)
print("courriel : ", utilisateur.courriel)
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Last Thing
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Thank you
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Questions ?
http://wirtel.be
[email protected] / @matrixise / github.com/matrixise
I am looking for jobs !
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