Variables, expressions, and statements,Values and types
變量，表達式和語句，值和類型
A value is one of the basic things a program works with, like a letter or a number. The values we have seen so far are 1, 2, and "Hello, World!"
值是程序使用的基本內容之一，例如字母或數字。到目前為止，我們看到的值為1、2和“ Hello，World！”。
These values belong to different types: 2 is an integer, and "Hello, World!" is a string, so called because it contains a "string" of letters. You (and the interpreter) can identify strings because they are enclosed in quotation marks.
這些值屬於不同的類型：2是整數，“ Hello，World！”是字符串，之所以稱為字符串是因為它包含字母的“字符串”。您（和解釋器）可以識別字符串，因為它們用引號引起來。
The print statement also works for integers. We use the python command to start the interpreter.
print語句也適用於整數。我們使用python命令啟動解釋器。
If you are not sure what type a value has, the interpreter can tell you.
如果您不確定值的類型，解釋器可以告訴您。
Not surprisingly, strings belong to the type str and integers belong to the type int. Less obviously, numbers with a decimal point belong to a type called float, because these numbers are represented in a format called floating point
毫不奇怪，字符串屬於str類型，而整數屬於int類型。不太明顯的是，帶小數點的數字屬於稱為浮點的類型，因為這些數字以稱為浮點的格式表示
What about values like "17" and "3.2"? They look like numbers, but they are in quotation marks like strings.
那麼“ 17”和“ 3.2”之類的值呢？它們看起來像數字，但用引號引起來，例如字符串。
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>>> type('17')
>>> type('3.2')
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They're strings.
他們是字符串。
When you type a large integer, you might be tempted to use commas between groups of three digits, as in 1,000,000. This is not a legal integer in Python, but it is legal:
當您輸入一個大整數時，您可能會想在三位數的組之間使用逗號，例如1,000,000。在Python中這不是合法的整數，但它是合法的：
Well, that's not what we expected at all! Python interprets 1,000,000 as a comma-separated sequence of integers, which it prints with spaces between.
好吧，這根本不是我們所期望的！ Python將1,000,000解釋為以逗號分隔的整數序列，並在其之間打印出空格。
This is the first example we have seen of a semantic error: the code runs without producing an error message, but it doesn't do the "right" thing.
這是我們看到的第一個語義錯誤示例：代碼運行時未產生錯誤消息，但沒有做“正確的”事情。
Variables 變數
One of the most powerful features of a programming language is the ability to manipulate variables. A variable is a name that refers to a value.
編程語言最強大的功能之一就是能夠操縱變量。變量是引用值的名稱。
An assignment statement creates new variables and gives them values:
賦值語句創建新變量並為其提供值：
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>>> message = 'And now for something completely different'
>>> n = 17
>>> pi = 3.1415926535897931
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This example makes three assignments. The first assigns a string to a new variable named message; the second assigns the integer 17 to n; the third assigns the (approximate) value of π to pi.
本示例進行了三個分配。第一個將字符串分配給一個名為message的新變量；第二個將整數17分配給n；第三個將π的（近似）值分配給pi。
To display the value of a variable, you can use a print statement:
要顯示變量的值，可以使用打印語句：
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>>> print(n)
17
>>> print(pi)
3.141592653589793
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The type of a variable is the type of the value it refers to.
變量的類型是它所引用的值的類型。
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>>> type(message)
<class 'str'>
>>> type(n)
<class 'int'>
>>> type(pi)
<class 'float'>
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