The document discusses various programming languages, primarily focusing on Python and its features such as type checking with mypy, data handling with libraries like NumPy and pandas, and integration with Haskell. It covers comparisons of typing systems, including dynamic and static typing, and looks at related frameworks and libraries. Additionally, it references potential type errors in Python functions and performance comparisons with other languages.

1. Python
(2018-02-27)
Masahiro Sakai ( )
PYTHON

2. • Twitter: @masahiro_sakai
github: https://github.com/msakai/
G+: https://plus.google.com/+MasahiroSakai
• :
( )
• :
– ( Haskell)
–
–

3. •
• Python
• Python
•
……

4. • Haskell
– Haskell ( )
• Ruby
–
( Python )
– Ruby-GNOME2
• Python
– Chainer + α
– PyPI

5. DISCLAIMER
•
Python
–
–
–
• Python
–

6. •
•
•
•

8. •
– R MATLAB
•
– numpy/scipy, pandas, scikit-learn, matplotlib, Jupyter
Notebook,
–

9. Python
• ……
Python
• ) numpy.array ==
– numpy …
– Python
⇒
– sorted([np.zeros(2), np.zeros(2)])
• ( collections-extended
RangeMap )

10. : ……
• ……
•
……
• ) pandas itertuples
type(next(pd.DataFrame({"x" + str(i): [i] for i in range(253)}).itertuples()))
#=> pandas.core.frame.Pandas
type(next(pd.DataFrame({"x" + str(i): [i] for i in range(254)}).itertuples()))
#=> tuple

12. : Lisp-1
•
– Scheme, JavaScript
– Common Lisp, Ruby Lisp-2 ( )
•
Python Ruby
obj.foo(args) obj.foo(args)
( ) obj.foo() obj.foo(), obj.foo
obj.foo obj.method(:foo)
m(args) m.call(args), m[args]

13. : Lisp-1
• ……
→
→
• Ruby Lisp-2
•
•
Python Ruby
obj.foo(…) obj.foo(…), obj.foo …
( ) obj.foo() obj.foo(), obj.foo
obj.foo obj.method(:foo)
m(…) m.call(…), m[…]

14. • (PEP 484)
• mypy
def greeting(name: str) -> str:
return 'Hello ' + name
print(greeting(0))
# => error: Argument 1 to "greeting" has incompatible
type "int"; expected "str"

15. • Haskeller
–
–
•
– →
• Python Haskell
–
• List Tuple List
……

16. • (gradual typing)
– (dynamic typing) (static typing)
– Jeremy G. Siek and Walid Taha, Gradual Typing for Functional Languages, in
Proceedings of the 2006 Scheme and Functional Programming Workshop
•
– dynamic type: Any … Any
– type consistency relation: A B
• A = B Any
( : int→Any Any→str)
–
int ⊑ Any ⊑ str
•
(1)

17. (2)
•
– Python (mypy), TypeScript, Closure, Hack, Flow, C#?
–
• Python
–
• Python (mypy)
• ……
– (Any )
• e.g. Blame Calculus ( )
• Python (mypy)

18. • :
• (np.array, chainer.Variable )
⇒
• shape
– shape
•
( : forward backward )
(1)
def __call__(self, x : np.array) -> np.array:

19. • shape Array(m,n,o)
……
– reshape
⇒ (c.f. )
– Haskell hmatrix API †
……
•
(2)
† https://hackage.haskell.org/package/hmatrix-0.18.2.0/docs/Numeric-LinearAlgebra-Static.html

20. : Chainer
• Chainer
DSL
–
–
type_check.expect(in_types[0].shape == in_types[1].shape)
Expect: in_types[0].shape == in_types[1].shape
Actual: (3,) != (2,)
http://blog.unnono.net/2015/10/chainer-typecheck.html

21. (3)
•
•
…
•

23. • CPython
• GPU CPU
– Python
……
– NN CPU
– GPU
……

24. numpy
• numpy
• numpy
( numpy )
– : x[np.arange(x.shape[0])[:, None], p]
–
•

25. •
( 1 540 2.1GB )
parsy-1.1.0 290m7.032s
pyparsing-2.2.0 562m41.623s
funcparserlib-0.3.6 79m45.315s
megaparsec-5.3.1 (Haskell) 18m12.025s
attoparsec-0.13.1.0 (Haskell) 15m46.415s
: Python str Haskell
ByteString(bytes )

26. • :
–
–
……
• Cython
–
–

27. •
–
CPython
(Go )
• GIL (Global Interpreter Lock)
–
CPython
……
ONNX-Chainer ……

29. • Python
• Python
–
– Python
•