Architecture of CPython - Part 1

Transcript

1. Architecture of CPython
   the Bricks !
   PART 1
   by Stephane Wirtel
   PyCon.Canada 2016 - Toronto - 11/13/2016
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2. I am ... Stephane
   CPython contributor
   blah blah Python blah
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3. 3 / 94
   

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4. Agenda
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5. Agenda
   What is the Bytecode ?
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6. Agenda
   What is the Bytecode ?
   Code -> Bytecode
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7. Agenda
   What is the Bytecode ?
   Code -> Bytecode
   Bytecode
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8. Agenda
   What is the Bytecode ?
   Code -> Bytecode
   Bytecode
   .pyc file
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9. Agenda
   What is the Bytecode ?
   Code -> Bytecode
   Bytecode
   .pyc file
   Virtual Machine
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10. 10 / 94
    

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11. Bytecode
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12. Bytecode
    Instructions to follow
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13. Bytecode
    Instructions to follow
    Used by "Virtual" Machine
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14. Example of Bytecode
    In a restaurant... I am the "Virtual" Machine...
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15. Example of Bytecode
    In a restaurant... I am the "Virtual" Machine...
    SAY "Hello""
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16. Example of Bytecode
    In a restaurant... I am the "Virtual" Machine...
    SAY "Hello""
    SET CMD "Fish and Chips"
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17. Example of Bytecode
    In a restaurant... I am the "Virtual" Machine...
    SAY "Hello""
    SET CMD "Fish and Chips"
    ORDER CMD
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18. 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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19. 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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20. 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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21. 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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22. 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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23. 23 / 94
    

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24. Code -> Bytecode
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25. The Bricks!
    Developer
    Code
    Lexer/Parser AST
    Compiler Peepholer/Optimizer
    ByteCode Reader Inter pr eter
    Parsing
    Compiler
    VirtualMachine
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26. Code > Lexer > Parser > AST > Compiler
    >>> expr = 'x = 2 + 2'
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27. 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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28. 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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29. 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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30. 30 / 94
    

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31. Structure of a .pyc file
    Here is the source code
    print("Hello")
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32. 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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33. 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..60 6f64756c 653e0100 00007300 000000 |odule>....s....|
    6f
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34. 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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35. Structure of a .pyc file
    0 6 12
    Magic Number Time Stamp Header Size
    M ar shalling. . .
    M ar shalling. . .
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36. 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..60 6f64756c 653e0100 00007300 000000 |odule>....s....|
    6f
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37. 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..60 6f64756c 653e0100 00007300 000000 |odule>....s....|
    6f
    0x160D0D0A -> Magic Number
    0x1B911558 -> Time Stamp
    0x0F000000 -> Header Size
    Marshalling in Blue is the code and the variables
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38. Structure of a .pyc file
    Magic Number
    0x160D0D0A is based on the version of Python
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39. 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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40. 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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41. 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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42. Structure of a .pyc file
    Marshalling
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43. Structure of a .pyc file
    Marshalling
    Specific format to Python
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44. Structure of a .pyc file
    Marshalling
    Specific format to Python
    Contains Python Objects (tuple, list, dict, set, number, string, ...)
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45. 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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46. Structure of a .pyc file
    Marshalling - TYPE_CODE - 'c'
    #define TYPE_CODE 'c'
    0 16 32
    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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47. 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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48. 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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49. 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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50. Structure of a .pyc file
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51. Structure of a .pyc file
    Header
    
    3.5.0
    2016-11-09T11:31:0815
    
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52. 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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53. 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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54. Virtual Machine
    A Python Interpreter in 500 lines of code
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55. Virtual Machine
    Requirements ;-)
    Stack
    Frame
    Call Stack
    Bytecode
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56. Virtual Machine
    Stack
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57. Virtual Machine
    Stack
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58. 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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59. 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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60. Virtual Machine
    Call Stack
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61. 61 / 94
    

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62. Bytecode
    Instructions to follow
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63. Bytecode
    Instructions to follow
    Intermediate Representation of your Code
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64. Bytecode
    Instructions to follow
    Intermediate Representation of your Code
    Used by "Virtual" Machine
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65. Bytecode
    Instructions to follow
    Intermediate Representation of your Code
    Used by "Virtual" Machine
    Compact Code coded one "BYTE"
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66. 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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67. 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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68. 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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69. 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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70. 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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71. 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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72. 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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73. 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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74. 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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75. 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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76. 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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77. 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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78. 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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79. 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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80. 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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81. 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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82. 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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83. 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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84. 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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85. Read Python/ceval.c
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86. 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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87. 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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88. Welcome to the CPython World ;-)
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89. Just For Fun
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90. __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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91. 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', 'stephane@wirtel.be')
    print("nom : ", utilisateur.nom)
    print("courriel : ", utilisateur.courriel)
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92. Last Thing
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93. 92 / 94
    

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94. Thank you
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95. Questions ?
    http://wirtel.be
    stephane@wirtel.be / @matrixise / github.com/matrixise
    I am looking for jobs !
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