python for문

for <원소> in <목록>:

Python은 for in 문만 있음.

<원소> loop variable. <목록>객체내에 원소들이 하나씩 할당
<목록> 거의 모든 타입 사용 . list, tuple, string, iterator, generator, range()와 len() 내장 함수

>>>for item in iterable:
     반복할 구문

>>> for letter in ['A', 'B', 'C']:
...     print(letter)
...
A
B
C


# loop가 돌면서 어떻게 index와 element에 동시에 접근가능할까. => enumerate()활용

>>> for entry in enumerate(['A', 'B', 'C']):
        print(entry)
(0, 'A')
(1, 'B')
(2, 'C')
>>> for i, letter in enumerate(['A', 'B', 'C']):
        print(i, letter)
0 A
1 B
2 C
>>> for i, letter in enumerate(['A', 'B', 'C'], start=6):
        print(i, letter)
6 A
7 B
8 C

>>> # iter() 작동원리
>>> iter_letters = iter(['A', 'B', 'C'])
>>> next(iter_letters)
'A'
>>> next(iter_letters)
'B'
>>> next(iter_letters)
'C'

>>> # enumerate() 작동원리
>>> iter_letters = iter(['A', 'B', 'C'])
>>> next(iter_letters)
(0, 'A')
>>> next(iter_letters)
(1, 'B')
>>> next(iter_letters)
(2, 'C')

iterable

list

val= [1,2,3]
### Int
for i in val:
    print(i)
# 1
# 2
# 3

### List
[i for i in val]

#[1, 2, 3, 4, 5, 6]

range

val = range(1,3)
for i in val:
    print(i)

enumerate 내장 함수로 for 루프 돌리기

myList  = [1,2,3]
myTuple = (1,2,3)
mySet   = {1,2,3}

myStr = "123"
myDict= {"1":'a', "2":'b', "3":'c'}

인덱스 번호와 컬렉션의 원소를 tuple형태로 반환 (일일이 세다)

for i in enumerate(myList):  print(i)
for i in enumerate(myTuple): print(i)
for i in enumerate(mySet):   print(i)
# (0, 1)
# (1, 2)
# (2, 3)

for i in enumerate(myStr):  print(i)
for i in enumerate(myDict): print(i)
# (0, '1')
# (1, '2')
# (2, '3')

https://www.daleseo.com/python-enumerate/

중첩루프

>>> apart = [[101, 102, 103, 104],
             [201, 202, 203, 204],
             [301, 302, 303, 304], 
             [401, 402, 403, 404]]
>>> for floor in apart:
... \tfor room in floor:
... \t\tprint("Newpaper delivery: ", room)
... 
Newpaper delivery:  101
Newpaper delivery:  102
Newpaper delivery:  103
Newpaper delivery:  104
Newpaper delivery:  201
Newpaper delivery:  202
Newpaper delivery:  203
Newpaper delivery:  204
Newpaper delivery:  301
Newpaper delivery:  302
Newpaper delivery:  303
Newpaper delivery:  304
Newpaper delivery:  401
Newpaper delivery:  402
Newpaper delivery:  403
Newpaper delivery:  404

while

>>> i = 0
>>> while i <= 9:
... \tprint(i)
... \ti = i +1
... 
0
1
2
3
4
5
6
7
8
9
>>> i
10

for and if in one line

python-for문-if문-한-줄로-코딩하기

v1 = list(range(10))
#[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

v2 = [list(range(10)), [10,11,12]]

for i in v1:
    print(i)
    
==> int 

for i in v2:
    for j in i :
        print(j)

if v < 6 :
    print(0)
else
    print(1)


if v < 6 :
    print(0)
elif v < 10 :
    print(1)
else :
    print(2)

for i in v :
    if i==6 :
        print(i)

[i for i in v1]


==> list

[ j for i in v2 for j in i]

print( 0 if v<6 else 1 )





print(0 if v<6 else 1 if v<10 else 2)

[i for i in v if i==6]