파이썬 보강¶
- 손고리즘ML
- 임은지
In [1]:
!ls files/
Guido_van_Rossum.jpg who_uses_Python.png
Brief history of Python¶
- Invented by Guido Van Rossum in early 90s
- Named after comedy group Monty Python
- First public release in 1991
- Open Source from beginning
- Managed by Python Software foundation (PSF)
Python Features¶
easy-to-learn###¶
python has relatively few keywords, simple structure, and a clearly defined syntax
Rapid development###¶
Python lets you get more done with less code and less time
Powerful standard library###¶
One of Python's greatest strengths is the bulk of the library is portable and cross-platform compatible on *nix and windows
Interactive mode###¶
Python interpreter lets you try out code right away in its interative mode
Portable###¶
Python can run on a wide variety of platforms
Dynamically typed###¶
Python is a dynamically typed langueages. Types are assigned at run-time
Using Python as a Calculator#¶
In [2]:
2+2
Out[2]:
4
In [3]:
7/3 # Integer division returns the floor:
Out[3]:
2
In [4]:
7/-3
Out[4]:
-3
Numbers¶
In [5]:
width = 20
height = 5*9
width * height
Out[5]:
900
In [6]:
x = y = z = 0 # Zero x, y and z
x
Out[6]:
0
In [7]:
y
Out[7]:
0
In [8]:
z
Out[8]:
0
In [9]:
#try to access an undefined variable
n
--------------------------------------------------------------------------- NameError Traceback (most recent call last) <ipython-input-9-0976a63577f7> in <module>() 1 #try to access an undefined variable ----> 2 n NameError: name 'n' is not defined
In [ ]:
a = 1.5 + 0.5j # j is imaginary
a.real
In [ ]:
a.imag
Strings#¶
In [10]:
'spam eggs'
Out[10]:
'spam eggs'
In [11]:
'doesn\'t'
Out[11]:
"doesn't"
In [12]:
"doesn't" # 짝이 맞아야 함.
Out[12]:
"doesn't"
In [13]:
'"yes"' # 겹쳐도 됨.
Out[13]:
'"yes"'
In [14]:
'\"yes\"' # 이스케이프 써도 됨.
Out[14]:
'"yes"'
In [15]:
'\"yes \'\"' # 두번 겹쳤을 때는 이스케이스 문자가 인식되지 않음.
Out[15]:
'"yes \'"'
In [16]:
# 줄바꿈을 위해 \n 을 씀
# escape sequence : \n \t \r \0 \\ \' \"
hello = "This\nis\nhello "
print hello
This is hello
In [17]:
# """ 또는 '''을 사용하여 줄바꿈을 유지
hello = """This
is
hello"""
print hello
This is hello
In [18]:
# 문자열 앞에 r을 붙이면 raw문자열을 만든다.
# 이스케이스 문자가 적용되지 않음.
hello = r"This\nis\nhello "
print hello
This\nis\nhello
String Concatenation¶
In [19]:
'str' 'ing' # This is ok
Out[19]:
'string'
In [20]:
# strip() : 문자열 양쪽 공백을 모두 지움.
'str'.strip() + 'ing' #This is ok
Out[20]:
'string'
In [21]:
print 'str'.strip() 'ing' # 문자열로 인식할 수 있음.
File "<ipython-input-21-536c70cca56b>", line 1 print 'str'.strip() 'ing' # 문자열로 인식할 수 있음. ^ SyntaxError: invalid syntax
String Indexing#¶
In [22]:
word = "helpA"
In [23]:
word[4]
Out[23]:
'A'
In [24]:
word[0:2]
Out[24]:
'he'
In [25]:
word[2:4]
Out[25]:
'lp'
In [26]:
word[:2]
Out[26]:
'he'
In [27]:
word[2:]
Out[27]:
'lpA'
Strings are Immutable!¶
In [28]:
word[0] = 'x'
--------------------------------------------------------------------------- TypeError Traceback (most recent call last) <ipython-input-28-d89b9f9f38d7> in <module>() ----> 1 word[0] = 'x' TypeError: 'str' object does not support item assignment
In [29]:
word[:1] = 'Splat'
--------------------------------------------------------------------------- TypeError Traceback (most recent call last) <ipython-input-29-f21641443054> in <module>() ----> 1 word[:1] = 'Splat' TypeError: 'str' object does not support item assignment
Indices May be Negative¶
In [30]:
word[-1] # The last character
Out[30]:
'A'
In [31]:
word[-2] # The last-but-one character
Out[31]:
'p'
In [32]:
word[-2: ] # The last two characters
Out[32]:
'pA'
In [33]:
word[:-2] # Everything except the last two characters
Out[33]:
'hel'
Lists#¶
- used to group together other values
- List items need not all have the same type
- The most versatile
In [34]:
a = ['spam', 'eggs', 100, 1234]
a
Out[34]:
['spam', 'eggs', 100, 1234]
In [35]:
a[ : ]
Out[35]:
['spam', 'eggs', 100, 1234]
In [36]:
a[2] = a[2] + 23
a
Out[36]:
['spam', 'eggs', 123, 1234]
First Steps toward Programming¶
In [37]:
# Fibonacci series:
# the sum of two elements defines the next
a, b = 0, 1
In [38]:
while b < 10:
print b
a, b = b, a+b
1 1 2 3 5 8
In [39]:
# 입력받기
# 1. input : 정수로 받아 옴.
# val = input("입력: ")
# val
# 2. raw_input : 문자열로 받아 옴.
# val = raw_input("입력: ")
# val
# ** input 에 존재하는 변수명을 입력하면 변수로 인식 ** #
# test = 'hello'
# val = input("입력: ")
# val
x = int(raw_input("Please enter an integer: "))
Please enter an integer: 42
In [40]:
if x < 0:
x = 0
print 'Negative changed to zero'
elif x == 0:
print 'Zero'
elif x == 1:
print 'Single'
else:
print 'More'
More
For Statement¶
In [41]:
# Measure some strings:
a = ['cat', 'window', 'defenestrate']
for x in a:
print x, ',' ,len(x)
cat , 3 window , 6 defenestrate , 12
For Statement with Shallow Copy¶
In [42]:
# list operation
# 맨 앞에 새 요소 추가
# a.insert(0, 'new')
# 맨 뒤에 새 요소 추가
# a.append('new')
# 맨 앞의 요소 제거
# a.pop(0)
# 맨 마지막 요소 제거d
# a.pop()
# ** pop은 요소를 제거한 후 그 요소를 반환함.
In [43]:
for x in a[:]: # for x in a:
if len(x) > 6: a.insert(0,x)
a
Out[43]:
['defenestrate', 'cat', 'window', 'defenestrate']
In [44]:
# python copy
# 1. shallow copy
# elements aren't copied
# list2 = list1[:]
# 2. deep copy
# import copy
# list2 = copy.deepcopy(list1)
Copying a list¶
In [45]:
colors1 = ['red', 'green']
colors2 = colors1
colors2 = ['yello', 'blue']
print colors1
['red', 'green']
In [46]:
colors1 = ['red', 'green']
colors2 = colors1
colors2 = 'blue'
colors1
Out[46]:
['red', 'green']
Copy with the Slice Operator¶
In [47]:
list1 = ['a', 'b', 'c', 'd']
list2 = list1[:]
list2[1] = 'x'
print list2
['a', 'x', 'c', 'd']
In [48]:
print list1
['a', 'b', 'c', 'd']
In [49]:
# 위의 예제는 얕은 복사를 수행하지만
# 리스트가 서브리스트를 가질 때는 포인터 문제가 생긴다.
lst1 = ['a', 'b', ['ab', 'ba']]
lst2 = lst1[:]
In [50]:
lst2[0] = 'c' # shallow
lst2[2][1] = 'd'
print lst1 # deep
['a', 'b', ['ab', 'd']]
Using the Method deepcopy from the Module copy#¶
In [51]:
from copy import deepcopy
lst1 = ['a', 'b', ['ab', 'ba']]
lst2 = deepcopy(lst1)
lst2[2][1] = "d"
lst2[0] = "c";
print lst2
['c', 'b', ['ab', 'd']]
In [52]:
print lst1
['a', 'b', ['ab', 'ba']]
Range Function¶
In [53]:
range(5, 10) # excep for las element
Out[53]:
[5, 6, 7, 8, 9]
In [54]:
range(0, 10, 3) # 3을 더하면서
Out[54]:
[0, 3, 6, 9]
In [55]:
# the else suite is executed after the for, but only if the for terminates normally (not by a break).for n in range (2,10):
# http://www.slideshare.net/helghareeb/python-tutorial-part-1?qid=75e5a1b1-d944-4c47-9cf3-d52e9db9ebd8&v=qf1&b=&from_search=2
for n in range(2,10):
for x in range(2, n):
if n % x ==0:
print n, 'quals', x, '*', n/x
break
else:
print n, 'is a prime number'
3 is a prime number 4 quals 2 * 2 5 is a prime number 5 is a prime number 5 is a prime number 6 quals 2 * 3 7 is a prime number 7 is a prime number 7 is a prime number 7 is a prime number 7 is a prime number 8 quals 2 * 4 9 is a prime number 9 quals 3 * 3
Pass¶
while True: pass
In [ ]:
Functions¶
In [56]:
def fib(n):
""" Print a Fibonacci series up to n"""
a, b = 0, 1
while a<n:
print a,
a , b = b , a+b
In [57]:
fib(2000)
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597
return Statement¶
In [58]:
def fib2 (n):
result = []
a, b = 0, 1
while a<n:
result.append(a)
a, b = b , a+b
return result
In [59]:
f100 = fib2(100)
f100
Out[59]:
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]
default Argument Value¶
In [60]:
def ask_ok(prompt, retries = 4, complaint="Yes or no, please!"):
while True:
ok = raw_input(prompt)
if ok in ('y', 'ye', 'yes'):
return True
if ok in ('n','no', 'nop', 'nope'):
return False
retries = retries -1
if retries < 0:
raise IOError('refusenik user')
print complaint
In [61]:
ask_ok('test')
testyes
Out[61]:
True
Keyword Arguments¶
In [62]:
def parrot(voltage, state='a stiff', action='voom', type='Norwegian Blue'):
print voltage
print state
print action
print type
In [63]:
parrot(1000) # 1 positional argument
1000 a stiff voom Norwegian Blue
In [64]:
parrot(voltage=1000) # 1 keyword argument
1000 a stiff voom Norwegian Blue
In [65]:
parrot(voltage=1000000, action= 'VOMMM') # 2 keyword arguments
1000000 a stiff VOMMM Norwegian Blue
In [66]:
parrot('a million', 'bereft of life', 'jump') # 3positional argument
a million bereft of life jump Norwegian Blue
In [67]:
parrot('a thousand', state='pushing up the daisies') # 1 positional, 1 keyword
a thousand pushing up the daisies voom Norwegian Blue
In [68]:
# parrot()
In [69]:
# parrot(voltage=5.0, 'dead')
In [70]:
# parrot(110, voltage=220)
In [71]:
#parrot(actor='John')
In [72]:
#The *args and **kwargs is a common idiom to allow arbitrary number of arguments
def cheeseshop(kind, *arguments, **keywords):
print kind
for arg in arguments:
print arg
print "-" * 40
keys = sorted(keywords.keys())
for kw in keys:
print kw, ":", keywords[kw]
In [73]:
cheeseshop("This is kind", "no keyword1", "no keyword2",
bKeyword = "1",
aKeyword = "2",
cKeyword = "3")
This is kind no keyword1 no keyword2 ---------------------------------------- aKeyword : 2 bKeyword : 1 cKeyword : 3
축약함수(Lambda)¶
함수를 한 줄만으로 만들 수 있게 함. lambda 인자 : 표현식
In [74]:
# 사용 후 바로 사라짐
(lambda x,y: x*y)(3,4)
Out[74]:
12
In [75]:
# 인자값을 미리 지정하여 함수생성
multi = lambda x=3, y=4: x*y
multi()
Out[75]:
12
In [76]:
# lambda
def make_incrementor(n):
#print n
#print x
return lambda x: x+ n
f = make_incrementor(42)
In [77]:
f(0)
Out[77]:
42
In [78]:
f(2)
Out[78]:
44
Documentation String¶
In [79]:
def my_function():
""" Do nothing"""
print "n"
pass
In [80]:
print my_function.__doc__
Do nothing
Data Structures - List¶
- list.append(x) Add an item to the end of the list.
- list.extend(L) Extend the list by appending all the items in the given list.
- list.insert(i,x) Insert an item at a given position. 1st : 이 곳에 삽입 즉, a.insert(0,X) 는 리스트의 맨 앞에 삽입 a. insert(len(a),x) 는 a.append(x)와 같다.
- list.remove(x) x 아이템이 발견되는 첫번째 요소를 삭제해라.
- list.pop([i]) i 위치에 있는 요소를 제거하고 반환
- list.index(x) x가 있는 첫번째 요소의 인덱스를 반환
- list.count(x) x가 있는 횟수를 반환
- list.sort() 정렬~~
- list.reverse() 역순으로 ~
In [81]:
# example
a = [ 1,1, 2, 3, 7,4]
print a.count(1), a.count('a')
2 0
In [82]:
a.insert(1,0)
In [83]:
a
Out[83]:
[1, 0, 1, 2, 3, 7, 4]
In [84]:
a.append(333)
In [85]:
a
Out[85]:
[1, 0, 1, 2, 3, 7, 4, 333]
In [86]:
a.index(1)
Out[86]:
0
In [87]:
a.remove(3)
In [88]:
a
Out[88]:
[1, 0, 1, 2, 7, 4, 333]
In [89]:
a.reverse()
In [90]:
a
Out[90]:
[333, 4, 7, 2, 1, 0, 1]
In [91]:
a.sort()
In [92]:
a
Out[92]:
[0, 1, 1, 2, 4, 7, 333]
Using List as a Stack¶
In [93]:
stack = [3, 4, 5]
In [94]:
stack.append(6)
In [95]:
stack.append(7)
In [96]:
stack
Out[96]:
[3, 4, 5, 6, 7]
In [97]:
stack.pop()
Out[97]:
7
In [98]:
stack
Out[98]:
[3, 4, 5, 6]
Using List as a Queue¶
In [99]:
from collections import deque
# Queue : 앞으로 삭제, 뒤로는 삽입
# Deque : 양방향 가능
In [100]:
queue = deque(["Kim", "Lim"])
queue.append("Lee")
queue.popleft()
Out[100]:
'Kim'
In [101]:
queue
Out[101]:
deque(['Lim', 'Lee'])
In [102]:
queue.appendleft("Park")
In [103]:
queue
Out[103]:
deque(['Park', 'Lim', 'Lee'])
In [104]:
queue.pop()
Out[104]:
'Lee'
filter¶
filter(function, sequence)
return : 함수에서 정해진 내용의 반환값을 sequence형식으로 반환함.
- 만약 입력되는 sequence값이 string or tuple 이면 같은 타입으로 반환하고,
- 그렇지 않을 경우, 항상 리스트를 반환한다.
In [105]:
def f(x) : return x%2 !=0 and x%3 !=0
In [106]:
filter(f, range(2, 25))
Out[106]:
[5, 7, 11, 13, 17, 19, 23]
Map¶
map(function, sequenc)
return : sequence를 모두 거치면서 함수의 내용을 수행, 반환 함
- sequence 가 두 개일 경우,
- sequence 끼리 일치하는 인자를 피연산자로 함수를 처리할 수 있음.
In [107]:
def cube(x) : return x*x*x
map(cube, range(1,11))
Out[107]:
[1, 8, 27, 64, 125, 216, 343, 512, 729, 1000]
In [108]:
seq = range(8)
def add(x,y) : return x+y
map(add, seq, seq)
Out[108]:
[0, 2, 4, 6, 8, 10, 12, 14]
In [109]:
def add(x,y) : return x+y
reduce(add, range(1,11))
Out[109]:
55
In [110]:
squares = [ x**2 for x in range(10)]
squares
Out[110]:
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
In [111]:
[(x,y) for x in [1,2,3] for y in [3,1,4] if x!=y]
Out[111]:
[(1, 3), (1, 4), (2, 3), (2, 1), (2, 4), (3, 1), (3, 4)]
Del ()¶
In [112]:
a = [-1, 2,3,4]
del a[0]
a
Out[112]:
[2, 3, 4]
In [113]:
del a[1:2]
a
Out[113]:
[2, 4]
Tuples and Sequences¶
In [114]:
t = 123, 321, 'hello'
t
Out[114]:
(123, 321, 'hello')
In [115]:
u = t, (1,2,3,4,5) # Tuples may be nested
u
Out[115]:
((123, 321, 'hello'), (1, 2, 3, 4, 5))
Comma at the end!¶
In [116]:
cate = 'hello', # note trailing comma
len(cate)
Out[116]:
1
In [117]:
cate
Out[117]:
('hello',)
Sets¶
- is an unordered collection with no duplicate elemnets.
- Basic use : membership testing & eliminating duplicate entries.
- support mathematical operations
union, intersection, difference, symmetric difference.
In [118]:
basket = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
fruit = set(basket) # create a set without duplicates
fruit
Out[118]:
{'apple', 'banana', 'orange', 'pear'}
In [119]:
'orange' in fruit # fast membership testing
Out[119]:
True
In [120]:
# Demonstrate set operations on unique letters from two words
a = set('abracadabra')
b = set('alacazam')
a
Out[120]:
{'a', 'b', 'c', 'd', 'r'}
In [121]:
a - b # letters in a but in b
Out[121]:
{'b', 'd', 'r'}
In [122]:
a | b # letters in either a or b
Out[122]:
{'a', 'b', 'c', 'd', 'l', 'm', 'r', 'z'}
In [123]:
a & b # letters in both a and b
Out[123]:
{'a', 'c'}
In [124]:
a ^ b # letters in a or b but not both
Out[124]:
{'b', 'd', 'l', 'm', 'r', 'z'}
Dictionaries¶
key: value
In [125]:
score = {'Kim' : 100, 'Lim':20}
score['Lee'] = 90
score
Out[125]:
{'Kim': 100, 'Lee': 90, 'Lim': 20}
In [126]:
score['Lim']
Out[126]:
20
In [127]:
del score['Lim']
score
Out[127]:
{'Kim': 100, 'Lee': 90}
In [128]:
score.keys()
Out[128]:
['Lee', 'Kim']
In [129]:
'Kim' in score
Out[129]:
True
Dict() constructor¶
In [130]:
dict( kim =100, lim=10, park = 30)
Out[130]:
{'kim': 100, 'lim': 10, 'park': 30}
Looping Techniques¶
In [131]:
for i, v in enumerate(['tic', 'tac' ,'toe']):
print i,v
0 tic 1 tac 2 toe
Looping over Two Sequences¶
In [132]:
questions = ['name', 'hobby']
answers = ['eunji', 'eating']
for q, a in zip(questions, answers):
print 'What is your {0}? It is {1}.'.format(q,a)
What is your name? It is eunji. What is your hobby? It is eating.
Loop in Reverse¶
In [133]:
for i in reversed(xrange(1, 10, 2)):
print i
9 7 5 3 1
Module¶
In [134]:
import fibo
In [135]:
fibo.fib(1000) # write
fibo.fib2(100) # return
1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987
Out[135]:
[1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]
In [136]:
fibo.__name__ # Within a module
# the module's name is available as the global variable __name__.
Out[136]:
'fibo'
Assign Local Name¶
In [137]:
fib = fibo.fib
fib(500)
1 1 2 3 5 8 13 21 34 55 89 144 233 377
In [138]:
from fibo import fib, fib2
fib(500)
1 1 2 3 5 8 13 21 34 55 89 144 233 377
In [139]:
from fibo import *
fib(500)
1 1 2 3 5 8 13 21 34 55 89 144 233 377
Compiled Python Files¶
- 프로그램 시작 시간을 줄이기 위해, 바이트 컴파일된 pyc 파일을 사용 가능하다.
컴파일 방법¶
- 특정 파일 컴파일
import py_compile py_compile.compile("spam.py")
- 모든 파일 컴파일
python -m compileall
파이은은 spam.py 파일이 있는 디렉토리에 spam.pyc 파일이 있다면 해당 파일이 spam 모듈의 바이트 컴파일된 버전이라고 가정한다.
만약 spam.py파일의 최종 수정 시각이 spam.pyc 파일에 기록되기 때문에, 둘이 다르다면 pyc 파일은 무시되어 py 파일만을 사용하게 된다.
pyc 파일은 플랫폼에 독립적이기 때문에 서로 다른 플랫폼에서 공유될 수 있다.
dir()¶
The built-in function dir() is used to find out which names a module defines.
In [140]:
import fibo, sys
dir(fibo)
Out[140]:
['__builtins__', '__doc__', '__file__', '__name__', '__package__', 'fib', 'fib2']
In [141]:
dir(sys)
Out[141]:
['__displayhook__', '__doc__', '__egginsert', '__excepthook__', '__name__', '__package__', '__plen', '__stderr__', '__stdin__', '__stdout__', '_clear_type_cache', '_current_frames', '_getframe', '_mercurial', 'api_version', 'argv', 'builtin_module_names', 'byteorder', 'call_tracing', 'callstats', 'copyright', 'displayhook', 'dont_write_bytecode', 'exc_clear', 'exc_info', 'exc_type', 'excepthook', 'exec_prefix', 'executable', 'exit', 'exitfunc', 'flags', 'float_info', 'float_repr_style', 'getcheckinterval', 'getdefaultencoding', 'getdlopenflags', 'getfilesystemencoding', 'getprofile', 'getrecursionlimit', 'getrefcount', 'getsizeof', 'gettrace', 'hexversion', 'last_traceback', 'last_type', 'last_value', 'long_info', 'maxint', 'maxsize', 'maxunicode', 'meta_path', 'modules', 'path', 'path_hooks', 'path_importer_cache', 'platform', 'prefix', 'ps1', 'ps2', 'ps3', 'py3kwarning', 'setcheckinterval', 'setdlopenflags', 'setprofile', 'setrecursionlimit', 'settrace', 'stderr', 'stdin', 'stdout', 'subversion', 'version', 'version_info', 'warnoptions']
str() , repr()¶
str : 사용자가 보기 쉬운 형태로 보여줄 때 사용하는 것
repr: 시스템(python interpreter)이 해당 객체를 인식할 수 있는 공식적인 문자열로 나타내 줄 때 사용하는 것
In [142]:
str(1.0/7.0)
Out[142]:
'0.142857142857'
In [143]:
repr(1.0/7.0)
Out[143]:
'0.14285714285714285'
Formatting Output¶
In [144]:
for x in range(1,11):
print repr(x).rjust(2), repr(x*x).rjust(3),
print repr(x*x*x).rjust(4)
1 1 1 2 4 8 3 9 27 4 16 64 5 25 125 6 36 216 7 49 343 8 64 512 9 81 729 10 100 1000
In [145]:
# rjust : 오른쪽 정렬
# ljust : 왼쪽 정렬
a = "123"
print a.rjust(10)
123
In [146]:
print a.rjust(10,'#')
#######123
In [147]:
for x in range(1,11):
print '{0:2d} {2:4d} {1:3d}'.format(x, x*x, x*x*x)
1 1 1 2 8 4 3 27 9 4 64 16 5 125 25 6 216 36 7 343 49 8 512 64 9 729 81 10 1000 100
In [148]:
f = open('./testFile', 'r') # write : w , bothe w+
print f
<open file './testFile', mode 'r' at 0x7fa068255540>
In [149]:
f.read() # 전체를 읽음.
Out[149]:
"(dp0\nS'lim'\np1\nI20\nsS'kim'\np2\nI80\ns."
In [150]:
f.read() # f.readlines()
Out[150]:
''
In [151]:
f = open('./testFile', 'r')
f.readline()
Out[151]:
'(dp0\n'
In [152]:
f.readline()
Out[152]:
"S'lim'\n"
In [153]:
f.readline()
Out[153]:
'p1\n'
In [154]:
f.readline()
Out[154]:
'I20\n'
In [155]:
# alternative method
f = open('./testFile', 'r')
for line in f:
print line,
(dp0 S'lim' p1 I20 sS'kim' p2 I80 s.
In [156]:
# Write to file
f = open('./testFile', 'w+')
f.write('This is a test\n')
f.readlines()
Out[156]:
[]
In [157]:
f.close()
#f.read()
Pickle Module¶
파이썬에서 만들어는는 것은 뭐든지 다 파일에 적을 수 있다.
In [171]:
import pickle
f = open('./testFile2','w')
users = {'kim':80, 'lim':20}
pickle.dump(users, f)
f.close()
In [172]:
f = open('./testFile2','r')
a = pickle.load(f)
print a
{'lim': 20, 'kim': 80}
In [1]:
#while True: print 'Hello world'
while True print 'Hello world'
File "<ipython-input-1-b4e7f45d347e>", line 2 while True print 'Hello world' ^ SyntaxError: invalid syntax
Exceptions¶
In [2]:
10 * (1/0)
--------------------------------------------------------------------------- ZeroDivisionError Traceback (most recent call last) <ipython-input-2-9ce172bd90a7> in <module>() ----> 1 10 * (1/0) ZeroDivisionError: integer division or modulo by zero
In [3]:
4 + spam*3
--------------------------------------------------------------------------- NameError Traceback (most recent call last) <ipython-input-3-6b1dfe582d2e> in <module>() ----> 1 4 + spam*3 NameError: name 'spam' is not defined
In [4]:
'2' +2
--------------------------------------------------------------------------- TypeError Traceback (most recent call last) <ipython-input-4-c84fbe601d35> in <module>() ----> 1 '2' +2 TypeError: cannot concatenate 'str' and 'int' objects
Handling Exceptions¶
In [5]:
while True:
try:
x = int(raw_input("Please enter a number: "))
break
except ValueError:
print "That was no valid number. Try again..."
Please enter a number: lis That was no valid number. Try again... Please enter a number: 1
Else¶
break 로 끝나지 않으면, else 아래의 코드를 실행시키다.
In [7]:
import sys
for arg in sys.argv[1:] :
try:
f = open(arg, 'r')
except IOError:
print 'cannot open',arg
else :
print arg, 'has', len(f.readlines()), 'lines'
f.close()
cannot open -f /home/lim/.ipython/profile_default/security/kernel-b9f480b6-e7a4-499e-bfe6-c536d5bc0f3a.json has 11 lines cannot open --profile-dir cannot open /home/lim/.ipython/profile_default
Another Exception¶
In [8]:
def this_fails():
x = 1/0
try:
this_fails()
except ZeroDivisionError as detail:
print 'Handling run-time error: ', detail
Handling run-time error: integer division or modulo by zero
Raise Exception¶
In [9]:
raise NameError('HiThere')
--------------------------------------------------------------------------- NameError Traceback (most recent call last) <ipython-input-9-93385ba972b1> in <module>() ----> 1 raise NameError('HiThere') NameError: HiThere
In [ ]: