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python course 1 week 7 For Loop

admin 11月 13, 2020 0

While and For loop in Python 3.

n = 5
while n > 0:
    print(n)
    n = n - 1
print('Blastoff!')
print(n)

# 5
# 4
# 3
# 2
# 1
# Blastoff!
# 0

‘break’

The ‘break’ statement ends the loop and jumps to the statement after the loop.

while True:
    line = input('> ')
    if line == 'done':
        break
    print(line)
print('Done!')

‘continue’

Go to the next iteration
The ‘continue’ statement quits the current iteration and goes to the next iteration.

while True:
    line = input('> ')
    if line[0] == '#':
        continue
    if line == 'done':
        break
    print(line)
print('Done')

# > # don't print this
# > done
# Done

For Loop

1
2
3

for i in [5, 4, 3, 2, 1]:
    print(i)
print('Done!')

‘in’

Like forEach

friends = ['Ann', 'Bob', 'Cathy']
for friend in friends:
    print('Merry Christmas', friend + '!')
print('Done')

# 'None' keyword: absense of value
# 'is': check if two objects refer to the same object
# 'is not': also a logical operator
# '==': check if two objects have the same value
found = False
min_new = None # we haven't see the value
print('Before', found)
for number in [2, 3, 34, 123, 100]:
    if min_new is None: # see the min first time
        min_new = number
    elif min_new > number:
        min_new = number
print('min_new:', min_new)