Python Basics
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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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标签：Basics,string,just,Python,value,rules,only 来源： https://blog.csdn.net/maxinec93/article/details/118633089