條件敘述與運算子

Python 入門（開發者向）

Jasmin Ludolf

Senior Data Science Content Developer

布林值

# Boolean variable
the_truth = True
print(the_truth)

True

用來做比較

運算子

比較運算子
- 符號或符號組合
- 用於比較數值
檢查兩者是否相等
- ==

檢查是否相等

# Compare if 2 is equal to 3
2 == 3

False

# Check that 2 is not equal to 3
2 != 3

True

常見情境：檢查登入資訊

數值比較運算子

# Is 5 less than 7?
5 < 7

True

# Is 5 less than or equal to 7?
5 <= 7

True

# Is 5 greater than 7?
5 > 7

False

# Is 5 greater or equal to 7?
5 >= 7

False

其他比較

# Is James greater than Brian
"James" > "Brian"

True

字串依字母順序比較

條件敘述

若滿足 if 條件就執行，否則略過

# Check pasta quantities
required_quantity = 500
pasta_quantity = 200


# Compare pasta quantities
if pasta_quantity >= required_quantity

條件敘述

若滿足 if 條件就執行，否則略過

# Check pasta quantities
required_quantity = 500
pasta_quantity = 200


# Compare pasta quantities
if pasta_quantity >= required_quantity:

條件敘述

若滿足 if 條件就執行，否則略過

# Check pasta quantities
required_quantity = 500
pasta_quantity = 200


# Compare pasta quantities
if pasta_quantity >= required_quantity:

    print("You have enough pasta!")

縮排

# Check pasta quantities
required_quantity = 500
pasta_quantity = 200


# Compare pasta quantities
if pasta_quantity >= required_quantity:

print("You have enough pasta!") # This line is not indented

    print("You have enough pasta!")
    ^
IndentationError: expected an indented block

Elif 敘述

# Check pasta quantities
required_quantity = 500
pasta_quantity = 200

# Compare pasta quantities
if pasta_quantity >= required_quantity:

    print("You have enough pasta!")

elif pasta_quantity >= 300:
    print("Nearly enough pasta. Try a smaller portion.")

elif 可依需要加入多個！

Else 敘述

# Check pasta quantities
required_quantity = 500
pasta_quantity = 200

# Compare pasta quantities
if pasta_quantity >= required_quantity:

    print("You have enough pasta!")

elif pasta_quantity >= 300:
    print("Nearly enough pasta. Try a smaller portion.")

# Otherwise...
else:
    print("Not enough pasta.")

Not enough pasta.

比較運算子小抄

運算子	功能
`==`	等於
`!=`	不等於
`>`	大於
`>=`	大於或等於
`<`	小於
`<=`	小於或等於

關鍵字	功能	用法
`if`	條件成立時執行	工作流程中的第一步
`elif`	否則再檢查條件	接在 `if` 之後
`else`	以上皆否則執行此動作	接在 `elif` 之後

一起來練習吧！

Python 入門（開發者向）