Python条件控制与循环

条件控制语句：if

循环语句：while、for

其他语句：continue、break、pass

1、if语句

# ================================
a = 1
if a < 2:
    print('true')
else:
    print('false')
# ================================
if a:
    print('true')
else:
    print('false')
# ================================
if a == 0:
    print('a = 0')
elif a == 1:
    print('a = 1')
elif a == 2:
    print('a = 2')
else:
    print('a为其他值')

2、while语句

# ===================================
a = 1
sum = 0
while a <= 100:
    sum += sum
    a += 1
print('1到100的和为：', sum)
# ===================================
a = 0
while a < 5:
    print('a小于5')
    a += 1
else:
    print('a大于等于5')
# ===================================
a = 0
while a < 5:
    a += 1
    if a == 2:
        continue
    if a == 4:
        break
    print(a, end=' ')

3、for语句

# ==================================
lst = ['aaa', 'bbb', 'ccc', 'ddd']
for s in lst:
    print(s, end=' ')
print()
# ==================================
lst = ['aaa', 'bbb', 'ccc', 'ddd']
for s in lst:
    if s == 'aaa':
        continue
    if s == 'ccc':
        break
    print(s, end=' ')
else:
    print('finish')
print()

4、pass语句

a = 0
if a == 0:
    pass
elif a == 1:
    pass
elif a == 2:
    pass
else:
    pass