# ================================

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')

# ===================================

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=' ')

# ==================================

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()

a = 0

if a == 0:

    pass

elif a == 1:

    pass

elif a == 2:

    pass

else:

    pass