Python Basics and Built-in Functions Link-优快云博客

本文介绍了Python编程中表达式的概念，包括数值类型（整数、浮点数）、字符串及其操作（如*用于重复）。还讨论了变量的使用，将其比喻为计算机内存中的值存储箱，强调变量赋值后旧值将被遗忘。遵循的变量命名规则包括单一单词、不包含空格、只能用字母、数字和下划线，并且不能以数字开头。此外，提到了注释的使用（#号开始）和不同类型的运算符，如算术运算符和字符串连接。文章还提及了函数的基本形式，如print()和input()，并建议查阅内置函数文档以获取更多扩展信息。

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These rules for putting operators and values together to form expressions are a fundamental part of Python as a programming language, just like the grammar rules that help us communicate.

[Python Tutor - Visualize Python]

Remember that expressions are just values combined with operators, and they always evaluate down to a single value. A data type，say,The Integer, Floating-Point, and String Data Types.–> int(), float()and str(’ '),

The Interger :-5,0,35, 1,2,3

Floating point:-0.25, 2.3, 1.75

Strings are like ‘a’, ‘bbb’, ‘Hello world!’, ‘5 dogs’ The single quote should be 2 in the begin and end of strings.If just type one,then it will shown SyntaxError: EOL while scanning string literal. Cuz (’) characters are the signals for Python to known the strings begins and ends.

The *operator can be used with only two numeric values (for multiplication), or one string value and one integer value (for string replication).

Storing Values in Variables,Imaging Variables as a store value box in computer’s memory.When a variable is assigned a new value, the old value is forgotten.

When name a variable,3 principle rules as follows:

1.It can be only one word with no spaces.

2.It can use only letters, numbers, and the underscore (_) character.

3.It can’t begin with a number.

(P.S. Variable names are case-sensitive that means WE,we,We are 3 difference variables.)

Tool: >>> interactive shell and file editor(or say text editors such as Notepad or TextMate)

The hash mark # is part of comments are use for recording the notes.

Different types of operators +, -, *, /, //, %, and **for math operations,

+and *for string operations.

When write a function name, the opening and closing parentheses() at the end identify it as the name of a function.such as print(),input(),and len() functions.

Extension of built-in functions check up->[Built-in Functions — Python 3.9.6 documentation]
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