Conditionals有條件的 << Previous Next >> List Less Than Ten列出少於十

Checking for equality and comparators in general檢查是否相等以及一般的比較器

A fundamental thing you want to do with your program is check whether some number is equal to another. Say the user tells you how many questions they answered incorrectly on a practice exam, and depending on the number of correctly-answered questions, you can suggest a specific course of action. For integers, strings, floats, and many other variable types, this is done with a simple syntax: ==. To explicitly check inequality, use !=.

if a == 3:

print("the variable has the value 3")

elif a != 3:

print("the variable does not have the value 3")

Notice how in this example, the condition is redundant. In the first condition we are checking whether the variable a has the value 3 and in the second, we are checking whether a does NOT have the value 3. However, if the first condition is not true (a is in fact not 3), then the second condition is by definition true. So a more efficient way to write the above conditional is like this:

if a == 3:

print("the variable has the value 3")

else:

print("the variable does not have the value 3")

The same equality / inequality comparisons work for strings.

您要對程序執行的基本操作是檢查某個數字是否等於另一個數字。假設用戶告訴您在練習考試中有多少個錯誤回答的問題，並且根據正確回答的問題數，您可以提出具體的操作建議。對於整數，字符串，浮點數和許多其他變量類型，這是通過簡單的語法完成的：==。要顯式檢查不平等，請使用!=。

  
if a == 3: 
  print("the variable has the value 3")
elif a != 3:
  print("the variable does not have the value 3")

請注意，在此示例中，條件是多餘的。在第一個條件中，我們正在檢查變量是否a具有值3，在第二個條件中，我們正在檢查變量是否a不具有值3。但是，如果第一個條件不成立（a實際上不是3），則第二個條件根據定義，條件是正確的。因此，編寫上述條件的更有效方法如下：

if a == 3: 
  print("the variable has the value 3")
else:
  print("the variable does not have the value 3")

相同的相等/不相等比較適用於字符串。

Conditionals有條件的 << Previous Next >> List Less Than Ten列出少於十