初学Python问题集锦之–while-loop与for-loop

while loops

定义与实例
i = 0
numbers = []

while i < 6:
print "At the top i is %d" % i
numbers.append(i)

i = i + 1
print "Numbers now: ", numbers
print "At the bottom i is %d" % i


print "The numbers: "

for num in numbers:
print num,

输出

At the top i is 0
Numbers now: [0]
At the bottom i is 1
At the top i is 1
Numbers now: [0, 1]
At the bottom i is 2
At the top i is 2
Numbers now: [0, 1, 2]
At the bottom i is 3
At the top i is 3
Numbers now: [0, 1, 2, 3]
At the bottom i is 4
At the top i is 4
Numbers now: [0, 1, 2, 3, 4]
At the bottom i is 5
At the top i is 5
Numbers now: [0, 1, 2, 3, 4, 5]
At the bottom i is 6
The numbers: 
0 1 2 3 4 5

for loops

定义和实例
elements = []

# then use the range function to do 0 to 5 counts
for i in range(0, 6):
print "Adding %d to the list." % i
# append is a function that lists understand
elements.append(i)

A&Q

What’s the difference between a for-loop and a while-loop?
answer:   
for-loop can only iterate (loop) “over” collections of things.
while-loop can do any kind of iteration (looping) you want. However, while-loops are harder to get right and you normally can get many things done with for-loops.

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