Python 내장 함수

파이썬 내장 함수
정보기술 시대에 유익한 파이썬 프로그래밍 – 제 6 강 (2)
동양미래대학교
2015.7
최용 <sk8er.choi@gmail.com>

내장 함수
Built-in Functions

Python3 내장 함수
Built-in Functi
ons
abs() dict() help() min() setattr()
all() dir() hex() next() slice()
any() divmod() id() object() sorted()
ascii() enumerate() input() oct() staticmethod()
bin() eval() int() open() str()
bool() exec() isinstance() ord() sum()
bytearray() filter() issubclass() pow() super()
bytes() float() iter() print() tuple()
callable() format() len() property() type()
chr() frozenset() list() range() vars()
classmethod() getattr() locals() repr() zip()
compile() globals() map() reversed() __import__()
complex() hasattr() max() round()
delattr() hash() memoryview() set()
https://docs.python.org/3/library/functions.html

abs()
>>> abs(-3)
3
>>> abs(-3.0)
3.0
>>> z = complex(1, 2)
>>> abs(z)
2.23606797749979

all()
>>> all([True, True, True])
True
>>> all([True, False, True])
False

any()
>>> any([True, False, True])
True
>>> any((False, False, False))
False

ascii()
>>> ascii('''Airbed
... Breakfast''')
"'AirbednBreakfast'"
>>> ascii('김치')
"'uae40uce58'"

bin()
>>> bin(1)
'0b1'
>>> bin(2)
'0b10'
>>> bin(3)
'0b11'
>>> bin(4)
'0b100'

bool()
>>> bool(True)
True
>>> bool(2 < 3)
True
>>> bool(1)
True
>>> bool(3 % 2)
True
>>> bool(not None)
True
>>> bool(False)
False
>>> bool(2 > 3)
False
>>> bool(0)
False
>>> bool(4 % 2)
False
>>> bool(None)
False
>>> bool()
False

bytearray()
>>> data = bytearray(b'Monty Python')
>>> data[5] = 33 # mutable
>>> data
bytearray(b'Monty!Python')
http://python3porting.com/problems.html#manipulating-binary-data
http://dabeaz.blogspot.kr/2010/01/few-useful-bytearray-tricks.html

bytes()
>>> b'Python'
b'Python'
>>> type(b'Python')
<class 'bytes'>
>>> b'파이썬'
File "<stdin>", line 1
SyntaxError: bytes can only contain ASCII literal characters.
>>> bytes('Python', 'utf-8')
b'Python'
>>> bytes('파이썬', 'utf-8')
b'xedx8cx8cxecx9dxb4xecx8dxac'

callable()
>>> def sum(x, y):
... return x + y
...
>>> callable(sum)
True
>>> x = 10
>>> callable(x)
False
>>> class MyClass:
... pass
...
>>> callable(MyClass)
True
>>> obj = MyClass()
>>> callable(obj)
False
http://joequery.me/code/python-builtin-functions/#callable

chr()
>>> chr(65)
'A'
>>> chr(97)
'a'
>>> chr(49)
'1'

classmethod()
>>> class Pizza:
... radius = 42
... @classmethod
... def get_radius(cls):
... return cls.radius
...
>>> Pizza.get_radius()
42
https://julien.danjou.info/blog/2013/guide-python-static-class-abstract-methods

compile()
>>> codeobj = compile('x = 2nprint("X is " + str(x))', # source
... 'fakemodule', # file name
... 'exec') # mode
>>> exec(codeobj)
X is 2
http://stackoverflow.com/questions/22443939/python-built-in-function-compile-what-is-it-used-for

complex()
>>> x = complex("4+2j")
>>> x
(4+2j)
>>> y = complex("4-5j")
>>> y
(4-5j)
>>> x+y
(8-3j)
>>> x*y
(26-12j)
>>> complex("4")
(4+0j) http://joequery.me/code/python-builtin-functions/#complex

delattr()
>>> class Employee:
... def __init__(self, name, salary):
... self.name = name
... self.salary = salary
...
>>> j = Employee("John", "2000$")
>>> j.salary
'2000$'
>>> delattr(j, "salary")
>>> hasattr(j, "salary")
False

dict()
>>> dict()
{}
>>> dict( [[1, 'a'], [2, 'b'], [3, 'c']] )
{1: 'a', 2: 'b', 3: 'c'}
>>> dict( ((1, 'a'), (2, 'b'), (3, 'c')) )
{1: 'a', 2: 'b', 3: 'c'}

dir()
>>> class Shape:
... def __dir__(self):
... return ['area', 'perimeter', 'location']
...
>>> s = Shape()
>>> dir(s)
['area', 'location', 'perimeter']
>>> import struct
>>> dir(struct)
['Struct', '__all__', '__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__', '__pack
age__', '__spec__', '_clearcache', 'calcsize', 'error', 'iter_unpack', 'pack', 'pack_into', 'unpack', 'unpack_
from']

divmod()
>>> divmod(7, 3)
(2, 1)
>>> divmod(8.4, 4.2)
(2.0, 0.0)
>>> divmod(8.5, 4.2)
(2.0, 0.09999999999999964)

enumerate()
>>> seasons = ['Spring', 'Summer', 'Fall', 'Winter']
>>> list(enumerate(seasons))
[(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')]
>>> list(enumerate(seasons, start=1))
[(1, 'Spring'), (2, 'Summer'), (3, 'Fall'), (4, 'Winter')]

eval()
>>> x = 1
>>> eval('x + 1')
2
>>> y = eval('x + 2')
>>> y
3
>>> a = 10
>>> b = 5
>>> D = {'a': 2, 'b': 3}
>>> eval('a + b')
15
>>> eval('a + b', D)
5

exec()
>>> a = 3
>>> exec('b = 2') # eval()과 달리, 값을 리턴하지 않음
>>> exec('c = a + b')
>>> c
5

filter()
>>> N = range(1, 11)
>>> Even = list()
>>> for n in N:
... if n % 2 == 0:
... Even.append(n)
...
>>> Even
[2, 4, 6, 8, 10]
>>> Odd = list(filter(lambda x: x % 2, N))
>>> Odd
[1, 3, 5, 7, 9]

float()
>>> float(1)
1.0
>>> float(1.234)
1.234
>>> float('+1.23')
1.23
>>> float(' -12345n')
-12345.0
>>> float('1e-003')
0.001
>>> float('+1E6')
1000000.0
>>> float('-Infinity')
-inf

format()
>>> L = [['a', 123], ['by', 45.6], ['cow', 7.89]]
>>> for s, n in L:
... print(s, n)
...
a 123
by 45.6
cow 7.89
>>> for s, n in L:
... print(format(s, '^10') + '|' + format(n, '<.2f'))
...
a |123.00
by |45.60
cow |7.89 http://joequery.me/code/python-builtin-functions/#format

frozenset()
set
• mutable
• add()
• remove()
frozenset
• immutable: 생성된 이후에는
내용을 변경할 수 없음

getattr()
>>> class MyClass:
... x = 0
... y = 1
...
>>> myobj = MyClass()
>>> getattr(myobj, 'x')
0

globals()
>>> globals()
{'__name__': '__main__', '__builtins__': <module
'builtins' (built-in)>, '__loader__': <class '_frozen_
importlib.BuiltinImporter'>, '__spec__': None, '__
doc__': None, '__package__': None}
>>> balance = 200
>>> cost = 50
>>> globals()
{'__name__': '__main__', '__builtins__': <module
'builtins' (built-in)>, 'balance': 200, '__loader__': <
class '_frozen_importlib.BuiltinImporter'>, '__spe
c__': None, '__doc__': None, '__package__': Non
e, 'cost': 50}
>>> eval('balance - cost')
150
>>> mylocals = {'cost': 75}
>>> eval('balance - cost', mylocals)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 1, in <module>
NameError: name 'balance' is not defined
>>> eval('balance - cost', globals(), mylocals)
125
http://joequery.me/code/python-builtin-functions/#eval

hasattr()
>>> class MyClass:
... x = 0
... y = 1
...
>>> myobj = MyClass()
>>> hasattr(myobj, 'y')
True
>>> hasattr(myobj, 'z')
False

hash()
>>> hash('One little, two little, three little indians')
-7814896826006998464
>>> hash('indian')
-8497506485016990678
>>> hash('boy')
2674027540618413217
>>> hash('One little, two little, three little indians')
-7814896826006998464
>>> hash('indian')
-8497506485016990678
http://stackoverflow.com/questions/7646520/is-this-an-appropriate-use-of-pythons-built-in-hash-function
http://www.pythoncentral.io/hashing-strings-with-python/

help()
>>> help(eval)
Help on built-in function eval in module builtins:
eval(...)
eval(source[, globals[, locals]]) -> value
Evaluate the source in the context of globals and locals.
The source may be a string representing a Python expression
or a code object as returned by compile().
The globals must be a dictionary and locals can be any mapping,
defaulting to the current globals and locals.
If only globals is given, locals defaults to it.

hex()
>>> for n in range(20):
... print(hex(n))
...
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
0x8
0x9
0xa
0xb
0xc
0xd
0xe
0xf
0x10
0x11
0x12
0x13

id()
>>> a = 1
>>> b = 2
>>> L = [a, b]
>>> M = L
>>> id(L[0])
4297370688
>>> id(M[0])
4297370688

input()
>>> s = input('Type any string: ')
Type any string: Python
>>> print(s)
Python

int()
>>> n = int(input('Type any number: '))
Type any number: 3
>>> print(n * n)
9

isinstance()
>>> class Human:
... pass
...
>>> me = Human()
>>> isinstance(me, Human)
True
>>> class Robot:
... pass
...
>>> you = Robot()
>>> isinstance(you, Human)
False
>>> class Vehicle:
... pass
...
>>> class Car(Vehicle):
... pass
...
>>> mycar = Car()
>>> isinstance(mycar, Car)
True
>>> isinstance(mycar, Vehicle)
True

issubclass()
>>> class Vehicle:
... pass
...
>>> class Car(Vehicle):
... pass
...
>>> issubclass(Car, Vehicle)
True

iter()
>>> my_list = [5, 1, 6, 3]
>>> my_iter = iter(my_list)
>>> next(my_iter)
5
>>> next(my_iter)
1
>>> next(my_iter)
6
>>> next(my_iter)
3

len()
>>> len('Python')
6
>>> len('파이썬')
3
>>> len([2, 3, 6, 4, 5, 20])
6

list()
>>> list([1, 2, 3])
[1, 2, 3]
>>> list((1, 2, 3))
[1, 2, 3]
>>> list('XYZxyz')
['X', 'Y', 'Z', 'x', 'y', 'z']

locals()
>>> def foo(arg): # 함수 foo는 로컬 네임스페이스에 두 개의 변수 arg와 x를 가짐
... x = 1
... print(locals())
...
>>> foo(7) # locals는 이름/값 사전을 리턴
{'x': 1, 'arg': 7}
>>> foo('bar')
{'x': 1, 'arg': 'bar'}
http://www.diveintopython.net/html_processing/locals_and_globals.html

map()
for … in …
>>> M = list()
>>> for x in range(1, 6):
... M.append(x % 2)
...
>>> M
[1, 0, 1, 0, 1]
map()
>>> map(lambda x: x % 2, range(1, 6))
<map object at 0x101a67d30>
>>> list(_)
[1, 0, 1, 0, 1]

max()
>>> max(1234, 234, 34, 4)
1234
>>> max([3, 9, 27])
27
>>> max('return')
'u'

memoryview()
>>> ba = bytearray(b'abcdefgh')
>>> mv = memoryview(ba)
>>> mv[4:6]
<memory at 0x0000000002BB7CC8>
>>> mv[4:6].tobytes()
b'ef'
>>> mv[4:6] = b'ZA'
>>> ba
bytearray(b'abcdZAgh')
http://eli.thegreenplace.net/2011/11/28/less-copies-in-python-with-the-buffer-protocol-and-memoryviews

min()
>>> min(1234, 234, 34, 4)
4
>>> min('invest')
'e'

next()
>>> my_list = [5, 1, 6, 3]
>>> my_iter = iter(my_list)
>>> next(my_iter)
5
>>> next(my_iter)
1
>>> next(my_iter)
6
>>> next(my_iter)
3

object()
>>> obj = object()
>>> type(obj)
<class 'object'>

oct()
>>> for n in range(1, 21):
... print(str(n) + ': ' + oc
t(n))
...
1: 0o1
2: 0o2
3: 0o3
4: 0o4
5: 0o5
6: 0o6
7: 0o7
8: 0o10
9: 0o11
10: 0o12
11: 0o13
12: 0o14
13: 0o15
14: 0o16
15: 0o17
16: 0o20
17: 0o21
18: 0o22
19: 0o23
20: 0o24

open()
>>> with open("test.txt", "wt") as out_file:
... out_file.write("This Text is going to out filenLook at it
and see!")
...
50
>>> with open("test.txt", "rt") as in_file:
... text = in_file.read()
...
>>> print(text)
This Text is going to out file
Look at it and see!
https://en.wikibooks.org/wiki/Non-Programmer%27s_Tutorial_for_Python_3/File_IO

ord()
>>> ord('A')
65
>>> ord('a')
97
>>> ord('1')
49

print()
>>> print('Python 3.4')
Python 3.4
>>> print('Python', '3.4')
Python 3.4
>>> print('Python', '3.4', sep='
')
Python 3.4
>>> print('Python', '3.4', sep='
_')
Python_3.4
>>> for x in range(3):
... print(x, end='n')
...
0
1
2
>>> for x in range(3):
... print(x, end='t')
...
0 1 2 >>>

property()
class C:
def __init__(self):
self._x = None
@property
def x(self):
"""I'm the 'x'
property."""
return self._x
@x.setter
def x(self, value):
self._x = value
@x.deleter
def x(self):
del self._x
>>> c = C()
>>> c.x = 10
>>> print(c.x)
10
>>> del c.x
>>> help(C)
Help on class C in module __main__:
class C(builtins.object)
| Methods defined here:
|
| __init__(self)
|
| -----------------------------------------------------------
-----------
| Data descriptors defined here:
|
| __dict__
| dictionary for instance variables (if defined)
|
| __weakref__
| list of weak references to the object (if defined)
|
| x
| I'm the 'x' property.

range()
>>> range(10)
range(0, 10)
>>> list(range(5))
[0, 1, 2, 3, 4]
>>> tuple(range(5))
(0, 1, 2, 3, 4)
>>> for x in range(0, 10, 2):
... print(x)
...
0
2
4
6
8
>>> for y in range(10, 0, -1):
... print(y)
...
10
9
8
7
6
5
4
3
2
1

repr()
>>> repr('''Airbed
... Breakfast''')
"'AirbednBreakfast'"
>>> repr('김치')
"'김치'"

reversed()
>>> reversed([0, 1, 2, 3, 4])
<list_reverseiterator object at 0x101a67c50>
>>> list(reversed([0, 1, 2, 3, 4]))
[4, 3, 2, 1, 0]

round()
>>> round(3.1415)
3
>>> round(3.1415, 2)
3.14

set()
>>> A = set([n for n in range(2, 31, 2)])
>>> 4 in A
True
>>> len(A)
15
>>> A.add(32)
>>> A
{32, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26,
28, 30}
>>> {4, 8, 12}.issubset(A)
True
>>> {4, 8, 12} < A
True
>>> B = set([n for n in range(3, 31,
3)])
>>> C = A.intersection(B)
>>> C
{24, 18, 12, 6, 30}
>>> A.issuperset(C)
True
>>> sorted(C)
[6, 12, 18, 24, 30]
>>> D = A.union(B)
>>> D
{2, 3, 4, 6, 8, 9, 10, 12, 14, 15,
16, 18, 20, 21, 22, 24, 26, 27, 28,
30}

setattr()
>>> class Employee:
... self.salary = salary
...
>>> j = Employee("John", "2000$")
>>> j.salary
'2000$'
>>> setattr(j, "salary", "3000$")
>>> j.salary
'3000$'
>>> setattr(j, "gender", "male")
>>> j.gender
'male'

slice()
>>> L = [0, 1, 2, 3, 4, 5, 6, 7,
8, 9]
>>> L[2:7]
[2, 3, 4, 5, 6]
>>> L[2:7:2]
[2, 4, 6]
>>> s = slice(2, 7)
>>> L[s]
[2, 3, 4, 5, 6]
>>> s = slice(2, 7, 2)
>>> L[s]
[2, 4, 6]

sorted()
>>> sorted([2, 3, 6, 4, 5, 20])
[2, 3, 4, 5, 6, 20]

staticmethod()
>>> class Util:
... @staticmethod
... def add(a, b):
... return a + b
...
>>> Util.add(2, 3)
5
http://pyengine.blogspot.kr/2011/08/staticmethod-vs-classmethod.html

str()
>>> str(1)
'1'
>>> str('a')
'a'
>>> str([1, 'a'])
"[1, 'a']"
>>> str(None)
'None'

super()
class LoggingDict(dict):
def __setitem__(self, key, value):
logging.info('Settingto %r' % (key, value))
super().__setitem__(key, value)
https://rhettinger.wordpress.com/2011/05/26/super-considered-super/

tuple()
>>> tuple([1, 2, 3])
(1, 2, 3)
>>> tuple((1, 2, 3))
(1, 2, 3)
>>> tuple('XYZxyz')
('X', 'Y', 'Z', 'x', 'y', 'z')

type()
>>> type(2)
<class 'int'>
>>> type('boy')
<class 'str'>
>>> type([2, 'boy'])
<class 'list'>
>>> type(None)
<class 'NoneType'>
>>> import calendar
>>> type(calendar)
<class 'module'>
>>> class MyClass:
... pass
...
>>> mc = MyClass()
>>> type(mc)
<class '__main__.MyClass'>

vars()
>>> class Employee:
... self._salary = salary
...
...
>>> j = Employee("John", "2000$")
>>> vars(j)
{'name': 'John', '_salary': '2000$'}

zip()
>>> x = [1, 2, 3]
>>> y = [4, 5, 6]
>>> zipped = zip(x, y)
>>> list(zipped)
[(1, 4), (2, 5), (3, 6)]
>>> list(zipped)
[]

__import__()
>>> from math import pi
>>> pi
3.141592653589793
>>> _temp = __import__('math', globals(), locals(), ['pi'], 0)
>>> pi = _temp.pi
>>> pi
3.141592653589793

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