2025-8-15

# for - repeating time is determined
# while() - repeating time is unknown
# case 1 : controller inside while loop
x = 1
while(True):
    print(x)
    x = x + 1
    #  add a controller
    if (x == 3):
        print (x)
        continue
        x = x + 1
    if (x == 7):
        break
else:
    print("loop exit normally")
# case 2 : controller at while conditional expession
while (x < 10):
    print("second while loop:",x)
    x = x + 1
else:
    print("second loop exit normally")
## for : loop iterable , range(), list[, tuple
#case 1 : loop a list
y = [1,2,3,4]
for i in y:
    print(i)
# case 2 : range() - range(start, end-1, step)
for i in range(0,10,1):
    print("loop",i)
for i in range(4,31,7): #[4,11,18,25]
    print(i)
for i in range(4,31): # step = 1
    print(i)
for i in range(31): # start = 0, step = 1
    print(i)
for i in range(30,0,-3): 
    print(i)
for i in range(30,33,2):
    print(i)   
#sub-list, slice() - 0:10:1
z = [0,1,2,3,4,5,6,7,8,9,10]
print(z[0:10:1])
print(z[:6]) # start = 0, 6-1 =5, step =1
print(z[3:1:1]) # empty []
print(z[-1:-4:-1])
a = "hello world"
print(a[-1:4:-1])