Python based learning Notes (a)
Compiled languages and interpreted languages:
Compiled language: reading the code executed again, typically generate a document such as a C language generated .h files to the computer to execute
Such as: C, C ++, C #, Java, Go
An interpreted language: reading an execution sentence does not generate files
Such as: Python, Javascript, ruby, PHP
Python environment installed:
1. Install the python interpreter (that is often said to install python) recommended py3, in 2020 py2 eliminated // soul
python interpreter installed Address: www.python.org (Downloads - the Window / MAC / Linux)
Checking the installation process may add python 3.x to Path (environmental settings do not need to follow)
Interpreter environment settings:
Right My Computer, Properties, Advanced System Settings, click Environment Variables (user variables for the current user, the system for all users, it is recommended to set the system user), the system variables inside Path, edit it, the position of the python interpreter installed, coupled with a semicolon (window7)
2. Install the IDE (PyCharm) // shell
pycharm installation path: www.jetbrains.com/pycharm/download/#section=windows
Recommended download Community Edition (free), students can not run with IDLE
Open, create a new project, set the path to create a project, select existing interpreter (select python.exe location interpreter)
Common built-in data types:
Numeric data types: int, bool (True, False), float, complex
Sequence Data Type: immutable: STR (string), tuple (tuple), bytes; Variable: List (list)
Data collection type: set (collection)
Dictionary data types: dict (dictionary)
Analyzing the data type of two built-in functions:
type () that is not the parent class is a subclass type, irrespective inheritance; for example: type (123) -> Back <class int>
the isinstance () will be considered a subclass of the parent class type, consider inheritance; example: isinstance (123, int) -> Returns True
Common operators:
Note: '/' is, floating point division, '//' is an integer division: rounded bits
input Output:
Input: input ()
Output: print ()
Branch statement:
1.if else/elif
2. The ternary operator
Example: num = 1 if a> b else 0 // If a> b returns 1, a≤b returns 0
loop statement:
1.for i in range（x1,x2）
2.while else /break/continue
String str
Format string:
Example 1: template = "% s demand correction move% s"% ( "Novice", "offer",)
Format: string% (variable)
Note: If the string is: "% s cell phone battery is 100%," the string has two percent, so use a variable to be wrong, it needs to be changed: "% s cell phone battery is 100 %%"
Advanced usage (using three quoted string line feed operation can be performed, more beautiful print format):
Example 2:. Template = "{0} and {1}" format ( 'google', 'chrom')
The format is: 'string' .format (variable)
expand:
template = "{name and {offer}}". format (name = 'students arrived early, and so advise seniors', offer = 'wish to have a graduate school recruit offer')
If you use a keyword parameter format (), then they will point to the value of the parameter name use
Str commonly used methods:
1. "xxx" .upper () // string in lowercase to uppercase characters the same, generally used for verification code Ignore case (conversion to uppercase or lowercase simultaneously)
2.“xxx”.lower（） //将字符串里的大写字母转为小写，字符不变，同上
3.“xxx”.isdigit（） //判断字符串是否为数字
4.“xxx”.rstrip（） //去除字符串右边的空格，一般用于登录
5.“xxx”.lstrip（） //去除字符串左边的空格
6.“xxx”.replace（‘老王，‘**’，1） //替换字符串，从字符串左向右找第一个老王替换成两*号，不写则所有老王都替换，一般用于敏感字体
7.“xxx”.split（‘，’，1） //分割字符串，从左向右找第一个逗号进行分割（rsplit（）从右向左），不写第二个参数找所有的，返回一个列表
常用的公共功能：
1.len（value） //计算长度
2.value[i] //索引 注：最末尾一个的索引也可以为-1，往前依次为-2，-3......
3.value[i1,i2,i3] //切片（i1≤序列＜i2，按i3的步长来取值） 前两个确定范围，后面按步长取
示例：value[-2：] //去最后两个字符
4399游戏测试工程师--笔试题：
试题：输入一个字符串，请将字符串反转：
小练习：
