# DAY 03 - if 陳述句
###### tags: `python教學` `print結尾語` `if/else` `九九乘法表`
## 縮排
在python中，縮排就跟C語言的大括號一樣
```python=
age = 21
if age >= 20 :
print("可以投票")
else :
print("不能投票")
```
### BMI計算機
```python=
#輸入
weight = int(input("輸入體重(公斤)"))
height = int(input("輸入身高(公分)"))
#換公尺
sq_h = (height / 100) ** 2
BMI = weight / sq_h
```
if 數字大小判斷
```python=
if BMI < 18.5 :
print("異常:過輕")
elif BMI < 24:
print("正常")
else:
print("異常",end=':')
if BMI < 27:
print("過重")
elif BMI < 30:
print("輕度肥胖")
elif BMI < 35:
print("中度肥胖")
else:
print("重度肥胖")
```
---
### 補充 - print結尾語
print函數定義(看看就好)
```python=
print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)
```
print目前常用到的只有結尾語
通常print沒有設定結尾語時，預設是使用\n(換行符號)
所以可以將print("",end = 'XX')裡的XX換成其他東西
e.g.
```python=
for i in range(1,10):
print(i,end = ',')
for i in range(1,10):
print(i,end = ' ')
```
輸出結果:
```python=
1,2,3,4,5,6,7,8,9,
1 2 3 4 5 6 7 8 9
```
---
### and & or
```python=
a = 5
b = 6
c = 8
if a>c and b>a:
print("兩個敘述句「都」對")
if a>c or b>a:
print("兩個敘述句「至少有一個」對")
```
---
### 補充 - 數字比較
python規範比較寬鬆 所以可以使用 a < b < c 這種連續比較數值的方式
e.g.
```python=
score = 87
if score == 100:
print("A+")
elif 90<=score<100:
print("A")
elif 80<=score<90:
print("B")
elif 70<=score<80:
print("C")
elif 60<=score<70:
print("D")
else:
print("F")
```
---
### if應用 - 偵測串列內是否有值
```python=
#空串列
students = []
if students: #偵測串列裡是否有值
print("有學生")
else:
print("串列是空的")
```
### if應用 - 偵測某值是否有在串列中
```python=
students = ["jack","rose","bonny","stan"]
studentA = "alan"
if studentA in students:
print("alan在串列中")
else:
print("alan不在串列中")
```
---
### inClass practice - 九九乘法表
輸出結果：
```python=
1 * 1 = 1 1 * 2 = 2 1 * 3 = 3 1 * 4 = 4 1 * 5 = 5 1 * 6 = 6 1 * 7 = 7 1 * 8 = 8 1 * 9 = 9
2 * 1 = 2 2 * 2 = 4 2 * 3 = 6 2 * 4 = 8 2 * 5 = 10 2 * 6 = 12 2 * 7 = 14 2 * 8 = 16 2 * 9 = 18
3 * 1 = 3 3 * 2 = 6 3 * 3 = 9 3 * 4 = 12 3 * 5 = 15 3 * 6 = 18 3 * 7 = 21 3 * 8 = 24 3 * 9 = 27
4 * 1 = 4 4 * 2 = 8 4 * 3 = 12 4 * 4 = 16 4 * 5 = 20 4 * 6 = 24 4 * 7 = 28 4 * 8 = 32 4 * 9 = 36
5 * 1 = 5 5 * 2 = 10 5 * 3 = 15 5 * 4 = 20 5 * 5 = 25 5 * 6 = 30 5 * 7 = 35 5 * 8 = 40 5 * 9 = 45
6 * 1 = 6 6 * 2 = 12 6 * 3 = 18 6 * 4 = 24 6 * 5 = 30 6 * 6 = 36 6 * 7 = 42 6 * 8 = 48 6 * 9 = 54
7 * 1 = 7 7 * 2 = 14 7 * 3 = 21 7 * 4 = 28 7 * 5 = 35 7 * 6 = 42 7 * 7 = 49 7 * 8 = 56 7 * 9 = 63
8 * 1 = 8 8 * 2 = 16 8 * 3 = 24 8 * 4 = 32 8 * 5 = 40 8 * 6 = 48 8 * 7 = 56 8 * 8 = 64 8 * 9 = 72
9 * 1 = 9 9 * 2 = 18 9 * 3 = 27 9 * 4 = 36 9 * 5 = 45 9 * 6 = 54 9 * 7 = 63 9 * 8 = 72 9 * 9 = 81
```
小提示
```python=
i," * ",j," = ",i*j
```
:::spoiler {state="close"} 解答
```python=
for i in range(1, 10): # i從1到9
for j in range(1, 10): # j從1到9
print(i ,'*', j ,'=' ,i*j,end=" ") #印出i*j=i*j
```
:::
---
### Homework - 印星星
每隔一行多兩個*
輸出結果：
```python=
*
***
*****
*******
```
:::spoiler 解答
7/10
:::
### Homework - 加法
https://zerojudge.tw/ShowProblem?problemid=a002
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