流程控制 - HackMD

{%hackmd @dzif24x25/IBXIWNXgTju0h2AKtSaLkA %} ###### tags: `Python` `流程控制` `if` `elif` `else` # 流程控制 ## 比較運算子 ### `>` 大於： ```python x = 3 y = 4 print(x > y) ``` 輸出結果 ```bash False ``` --- ### `<` 小於： ```python x = 3 y = 4 print(x < y) ``` 輸出結果 ```bash True ``` --- ### `>=` 大於或等於： ```python x = 4 y = 4 print(x >= y) ``` 輸出結果 ```bash True ``` --- ### `<=` 小於或等於： ```python x = 4 y = 4 print(x <= y) ``` 輸出結果 ```bash True ``` --- ### `==` 等於： ```python x = 4 y = 4 print(x == y) ``` 輸出結果 ```bash True ``` --- ### `!=` 不等於： ```python x = 4 y = 4 print(x != y) ``` 輸出結果 ```bash False ``` --- ## 邏輯運算子 ### `and` 而且： | `and`運算 | A: True | B: False | | -------- | -------- | -------- | | **B: True** | True | False | | **B: False** | False | False | ```python print('T and T =', True and True) print('T and F =', True and False) print('F and T =', False and True) print('F and F =', False and False) ``` 輸出結果 ```bash T and T = True T and F = False F and T = False F and F = False ``` --- ### `or` 或者： | `or`運算 | A: True | B: False | | -------- | -------- | -------- | | **B: True** | True | True | | **B: False** | True | False | ```python print('T and T =', True or True) print('T and F =', True or False) print('F and T =', False or True) print('F and F =', False or False) ``` 輸出結果 ```bash T and T = True T and F = True F and T = True F and F = False ``` --- ### `not` 非： | `not`運算 | A: True | A: False | | -------- | -------- | -------- | | | False | True | ```python print('not True =', not True) print('not False =', not False) ``` 輸出結果 ```bash not True = False not False = True ``` --- ## if敘述程式碼： ```python if 條件敘述: 程式區塊 ``` 流程圖： ```flow st=>start: if 開始 cond=>condition: 條件敘述 chunk=>operation: 程式區塊 en=>end: if 結束 st->cond cond(yes)->chunk->en cond(no)->en ``` :::info 註：若有程式區塊有多行，每一行程式的空格必須相同 ```python if 條件敘述: ****程式區塊 ****程式區塊 ****程式區塊 ``` 若有程式區塊只有單行，可以這樣寫： ```python if 條件敘述: 程式區塊 ``` ::: ## if...else敘述程式碼： ```python if 條件敘述: 程式區塊A else: 程式區塊B ``` 流程圖： ```flow st=>start: if...else 開始 cond=>condition: 條件敘述 chunkA=>operation: 程式區塊A chunkB=>operation: 程式區塊B en=>end: if...else 結束 st->cond cond(yes)->chunkA->en cond(no)->chunkB->en ``` ## if...elif...else敘述程式碼： ```python if 條件敘述1: 程式區塊1 elif 條件敘述2: 程式區塊2 elif 條件敘述3: 程式區塊3 else: 程式區塊n ``` 流程圖： ```flow st=>start: if...elif...else 開始 cond1=>condition: 條件敘述1 cond2=>condition: 條件敘述2 cond3=>condition: 條件敘述3 chunk1=>operation: 程式區塊1 chunk2=>operation: 程式區塊2 chunk3=>operation: 程式區塊3 chunkn=>operation: 程式區塊n en=>end: if...elif...else 結束 st->cond1 cond1(yes)->chunk1->en cond1(no)->cond2 cond2(yes)->chunk2->en cond2(no)->cond3 cond3(yes)->chunk3->en cond3(no)->chunkn->en ``` ### 範例 - 成績等級計算： ```python= score = int(input('請輸入您的分數：')) if score >= 90: level = '甲等' elif score >= 80: level = '乙等' elif score >= 70: level = '丙等' elif score >= 60: level = '丁等' else: level = '不及格' print('您的成績為', level) ``` 輸出結果： ![](https://i.imgur.com/Z20Fgdh.gif) ![](https://i.imgur.com/iCvi5KN.gif) :::info 點此前往簡報版： [https://hackmd.io/@dzif24x25/BJ4dPCSRo](https://hackmd.io/@dzif24x25/S1sgNYCRs) :::