typora/note/Python/控制语句.md

### 条件语句

- 正常写法

```python
a = 20
b = 10
if a==b:
    print("a == b")
elif a < b:
    print("a < b")
else:
    pring("a > b")
```

- 简写一行if

```python
a = 20
b = 10
if a > b: print("a > b")
```

- 简写一行if else

```python
a = 20
b = 10
print("A") if a > b else print("B")
```

- pass 语句，空if处理

```python
a = 66
b = 200

if b > a:
  pass
```



### and or

```python
a = 200
b = 66
c = 500
if a > b and c > a:
    print("Both conditions are True")

a = 200
b = 66
c = 500
if a > b or a > c:
    print("At least one of the conditions is True")
```



### while 循环

- break 终止循环
- continue 开始下一次循环

```python
i = 1
while i < 7:
  print(i)
  if i == 3:
    break
  i += 1

```

```python
i = 0
while i < 7:
  i += 1 
  if i == 3:
    continue
  print(i)
```

- else语句，条件不成立，执行else语句

```python
i = 1
while i < 6:
  print(i)
  i += 1
else:
  print("i is no longer less than 6")
```



### for 循环

- break
- continue

```python
fruits = ["apple", "banana", "cherry"]
for x in fruits:
  if x == "banana":
    continue
  print(x)

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  print(x) 
  if x == "banana":
    break
```

- range() 函数：返回一个数字序列，默认情况下从 0 开始，并递增 1（默认地），并以指定的数字结束

```python
for x in range(10):
  print(x)

for x in range(3, 10):
  print(x)

for x in range(3, 50, 6):
  print(x)
```

- else for循环不满足条件时执行else语句

```python
for x in range(10):
  print(x)
else:
  print("Finally finished!")
```

- pass语句

```python
for x in [0, 1, 2]:
  pass
```