[Python知识库]python条件控制与循环

1.条件控制

a = 111
if a < 10:
    if a == 1:
        print(1)
    elif a == 2:
        print(2)
    else:
        print(3456789)
elif a == 10:
    print(10)
else:
    print(11)

2.循环

• while循环

# while循环
a = 1
while a < 10:
    print(a)
    a += 2
# 输出13579

# 无限循环
while True:
    inp = input()
    print("输入的是", inp)

# while 后面的条件语句为 false 时，则执行 else 的语句块
a = 0
while a < 10:
    print(a)
    a += 3
else:
    print("end")

• for循环?

# for 循环可以遍历任何可迭代对象
list1 = [1, 2, 3, 4, 5, 6]
for i in list1:
    print(i)
else:
    print("end")

• range函数?

# range()函数遍历数字
for i in range(5):
    print(i, end=' ')  # 0 1 2 3 4
# 指定区间
for i in range(3, 9):
    print(i, end=' ')  # 3 4 5 6 7 8
# 指定增量
for i in range(3, 9, 2):
    print(i, end=' ')  # 3 5 7
# 负数
for i in range(-1, -10, -2):
    print(i, end=' ')  # -1 -3 -5 -7 -9
# 创建一个列表
list1 = list(range(5))
print(list1)  # [0, 1, 2, 3, 4]

• break与continue语句?

# break语句跳出当前循环体
n = 1
while n < 5:
    n += 1
    if n == 3:
        break
    print(n, end=' ')  # 2
# continue语句跳过当前循环块中的剩余语句，然后继续进行下一轮循环
m = 1
while m < 5:
    m += 1
    if m == 3:
        continue
    print(m, end=' ')  # 2 4 5

• pass语句

#  pass是空语句，是为了保持程序结构的完整性
for i in range(5):
    if i == 2:
        pass
    print(i, end=' ')  # 0 1 2 3 4