Python 学习第八天

（11）if 语句

x = int(input("Please enter an integer: "))
if x < 0:
    x = 0
    print('Negative changed to zero')
elif x == 0:
    print('Zero')
elif x == 1:
    print('Single')
else:
    print('More')

Please enter an integer: 42
More

（12）for 语句

#Measure some strings
words = ['cat','window','defenestrate']
for w in words:
    print(w,len(w))

cat 3
window 6
defenestrate 12

（13） range()函数

如果你需要遍历一个***，内置函数range()就派上用场了。

for i in range(5):
    print(i)
0
1
2
3
4

# print 5 through 9
for a in range(5,10):
    print(a)
# print 0 3 6 9
for b in range(0,10,3):
    print(b)
# print -10 -40 -70
for c in range(-10,-100,-30):
    print(c)

遍历一个列表，使用range()函数和len()函数。

a = ['Mary','had','a','little','lamb']
for i in range(len(a)):
    print(i,a[i])

0 Mary
1 had
2 a
3 little
4 lamb