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写优雅的代码

490 字

2 分钟

Python-分支和循环

2023-01-20

Python

参考资料：【Python教程】《零基础入门学习Python》最新版（2022年12月26日更新）

分支结构#

1. if结构#

1
if condition:
2
    statement_1(s1)
3
statement_2(s2)

2. if-else结构#

1
if condition:
2
    statement_1(s1)
3
else:
4
    statement_2(s2)
5
statement_3(s3)

3. if-elif-elif…(-else)结构#

1
if condition_1:
2
    statement_1(s1)
3
elif condition_2:
4
    statement_2(s2)
5
...
6
# else:
7
#     statement_n(sn)

4. oneline结构#

1
true_statement if condition else false_statement

循环结构#

1. while循环#

1.1 基本结构#

1
while condition:
2
    statement_1(s1)
3
statement_2(s2)

1.2 while-break结构#

1
while condition_1:
2
    statement_1(s1)
3
    if condition_2:
4
        break
5
    statement_2(s2)
6
statement_3(s3)

1.3 while-else结构#

1
while condition_1:
2
    statement_1(s1)
3
    if condition_2:
4
        break
5
    statement_2(s2)
6
else:
7
    statement_3(s3)
8
statement_4(s4)

仅在循环由condition_1退出时才执行else，由break终止则不执行else

1.4 嵌套结构#

1
i = 1
2
while i <= 9:
3
    j = 1
4
    while j <= i:
5
        print(j, "*", i, "=", j*i, end=" ")
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        j += 1
7
    print()
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    i += 1

1
1 * 1 = 1
2
1 * 2 = 2 2 * 2 = 4
3
1 * 3 = 3 2 * 3 = 6 3 * 3 = 9
4
1 * 4 = 4 2 * 4 = 8 3 * 4 = 12 4 * 4 = 16
5
1 * 5 = 5 2 * 5 = 10 3 * 5 = 15 4 * 5 = 20 5 * 5 = 25
6
1 * 6 = 6 2 * 6 = 12 3 * 6 = 18 4 * 6 = 24 5 * 6 = 30 6 * 6 = 36
7
1 * 7 = 7 2 * 7 = 14 3 * 7 = 21 4 * 7 = 28 5 * 7 = 35 6 * 7 = 42 7 * 7 = 49
8
1 * 8 = 8 2 * 8 = 16 3 * 8 = 24 4 * 8 = 32 5 * 8 = 40 6 * 8 = 48 7 * 8 = 56 8 * 8 = 64
9
1 * 9 = 9 2 * 9 = 18 3 * 9 = 27 4 * 9 = 36 5 * 9 = 45 6 * 9 = 54 7 * 9 = 63 8 * 9 = 72 9 * 9 = 81

2. for循环#

2.1 基本结构#

1
for identifier in iterable:
2
    statement_1(s1)
3
statement_2(s2)

1
sum = 0
2
for i in range(10):
3
    sum += i
4
print(sum)
5
# 45

2.2 range()函数#

range(stop)
range(start, stop)
range(start, stop, step)

1
for n in range(2, 10):
2
    for m in range(2, n):
3
            if n % m == 0:
4
                print(n, "=", m, "*", n // m)
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                break
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    else:
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        print(n, "is a prime number")

1
2 is a prime number
2
3 is a prime number
3
4 = 2 * 2
4
5 is a prime number
5
6 = 2 * 3
6
7 is a prime number
7
8 = 2 * 4
8
9 = 3 * 3

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3. if-elif-elif…(-else)结构