2.5 表达式和语句(Expressions and statements) 表达式(expression)是集值、变量和运算符的式子。单独值本身也可视为一个表达式,同理变量也是。例如: x是已赋值的变量。 语句(statement)是Python解释器可执行的代码块。如print和赋值语句。严格来说,表达式也是语句,但其区别在于表达式有值,而语句没有。 2.6 交互模式和...
1、当我们使用组合条件时,Python会进行短路计算。使用and操作时,它将返回第一个虚值或最后一项。使用or操作时,它会返回第一个真值或最后一项。 2、表达式(expressions)和语句(statements)不同。赋值语句(assignment statement)不会产生任何值。但是,赋值表达式(嗄ssignment expression)在分配变量的同时还能求值。 3、当...
在一些其他语言中,^用来表示幂运算,但是在Python中,它是一个位运算符,叫做XOR。本书中没有涉及到位运算,但是你可以去维基百科阅读相关资料http://wiki.python.org/moin/BitwiseOperators。 在Python 2 中,除法操作符结果有时候并不是你需要的: >>> minute = 59 >>> minute/600 minute的值是59,通常59除以60...
5 Whitespace in Expressions and Statements ·括号两侧、冒号,分号之前、’不用空格 ·关于切片的空格没看懂,大体是要统一、可以看作二元操作符 ·总是在 =(赋值), += ,-=,==,<,>,!=,<=,>=,in,not in, is,is not, and or not,->等二元操作符两侧加空格 ·当有多级优先级运算的时候,在最低级...
表达式和语句 Expressions and Statements Python之禅写到:“应该有一种,且最好是唯一的方法去实现” PEP 8尝试在表达式和语句中遵循该风格。 • 使用内部否定(if a is not b)而不是外否定(if not a is b) •不要使用长度==0(if len(somelist) == 0)的方式判断容器或序列为空,而是使用if not some...
2、语法:(True_statements) if (expressions) else (False_statements) expressions:待判断的表达式 True_statements:若expression判断为True,则执行此语句 False_statements:若expression判断为False,则执行此语句 3、if 语句支持嵌套 age = int(input("请输入您的年龄: ")) # input 18 ...
Python x, y = 3, 8 if x = y: print(f"x and y are equal ({x = }, {y = })") Unlike the C example, this Python code gives you an explicit error instead of a bug.The distinction between assignment statements and assignment expressions in Python is useful in order to avoid ...
(any section of the code that evaluates to a value), the returned value is assigned to the record automatically. For input records this is required. For output records the return value is optional, which allows them to execute arbitrary Python expressions or statements (section of code that ...
Statements contain expressions. Expressions create and process objects. The discussion of modules in Chapter 3 introduced the highest level of this hierarchy. This part’s chapters begin at the bottom, exploring both built-in objects and the expressions you can code to use them. ...
· All the essential Python keywords, operators, statements, and expressions needed to fully understand exactly what you’re coding and why - making programming easy to grasp and less frustrating · You will learn the answers to questions like What is the Python For Loop, what is Python used ...