一 环境与编译器
1.版本选择3.9.6
https://www.python.org/downloads/macos/
//选择3.9.6
2.编译器
https://www.jetbrains.com/pycharm/download/#section=mac
//右侧的免费社区版够用
3.文档
Python文档下载地址：
https://www.python.org/doc/
帮助：
很多程序可以执行一些操作来查看一些基本信息，Python可以使用-h参数查看各参数帮助信息：
zhaoxinglu@zhaoxingludeMBP ~ % python3 -h
usage: /Library/Developer/CommandLineTools/usr/bin/python3 [option] ... [-c cmd | -m mod | file | -] [arg] ...
Options and arguments (and corresponding environment variables):
-b : issue warnings about str(bytes_instance), str(bytearray_instance)
and comparing bytes/bytearray with str. (-bb: issue errors)
-B : don't write .pyc files on import; also PYTHONDONTWRITEBYTECODE=x
-c cmd : program passed in as string (terminates option list)
-d : turn on parser debugging output (for experts only, only works on
debug builds); also PYTHONDEBUG=x
-E : ignore PYTHON* environment variables (such as PYTHONPATH)
-h : print this help message and exit (also --help)
-i : inspect interactively after running script; forces a prompt even
if stdin does not appear to be a terminal; also PYTHONINSPECT=x
-I : isolate Python from the user's environment (implies -E and -s)
-m mod : run library module as a script (terminates option list)
-O : remove assert and __debug__-dependent statements; add .opt-1 before
.pyc extension; also PYTHONOPTIMIZE=x
-OO : do -O changes and also discard docstrings; add .opt-2 before
.pyc extension
-q : don't print version and copyright messages on interactive startup
-s : don't add user site directory to sys.path; also PYTHONNOUSERSITE
-S : don't imply 'import site' on initialization
-u : force the stdout and stderr streams to be unbuffered;
this option has no effect on stdin; also PYTHONUNBUFFERED=x
-v : verbose (trace import statements); also PYTHONVERBOSE=x
can be supplied multiple times to increase verbosity
-V : print the Python version number and exit (also --version)
when given twice, print more information about the build
-W arg : warning control; arg is action:message:category:module:lineno
also PYTHONWARNINGS=arg
-x : skip first line of source, allowing use of non-Unix forms of #!cmd
-X opt : set implementation-specific option. The following options are available:
-X faulthandler: enable faulthandler
-X oldparser: enable the traditional LL(1) parser; also PYTHONOLDPARSER
-X showrefcount: output the total reference count and number of used
memory blocks when the program finishes or after each statement in the
interactive interpreter. This only works on debug builds
-X tracemalloc: start tracing Python memory allocations using the
tracemalloc module. By default, only the most recent frame is stored in a
traceback of a trace. Use -X tracemalloc=NFRAME to start tracing with a
traceback limit of NFRAME frames
-X importtime: show how long each import takes. It shows module name,
cumulative time (including nested imports) and self time (excluding
nested imports). Note that its output may be broken in multi-threaded
application. Typical usage is python3 -X importtime -c 'import asyncio'
-X dev: enable CPython's "development mode", introducing additional runtime
checks which are too expensive to be enabled by default. Effect of the
developer mode:
* Add default warning filter, as -W default
* Install debug hooks on memory allocators: see the PyMem_SetupDebugHooks() C function
* Enable the faulthandler module to dump the Python traceback on a crash
* Enable asyncio debug mode
* Set the dev_mode attribute of sys.flags to True
* io.IOBase destructor logs close() exceptions
-X utf8: enable UTF-8 mode for operating system interfaces, overriding the default
locale-aware mode. -X utf8=0 explicitly disables UTF-8 mode (even when it would
otherwise activate automatically)
-X pycache_prefix=PATH: enable writing .pyc files to a parallel tree rooted at the
given directory instead of to the code tree
--check-hash-based-pycs always|default|never:
control how Python invalidates hash-based .pyc files
file : program read from script file
- : program read from stdin (default; interactive mode if a tty)
arg ...: arguments passed to program in sys.argv[1:]
Other environment variables:
PYTHONSTARTUP: file executed on interactive startup (no default)
PYTHONPATH : ':'-separated list of directories prefixed to the
default module search path. The result is sys.path.
PYTHONHOME : alternate <prefix> directory (or <prefix>:<exec_prefix>).
The default module search path uses <prefix>/lib/pythonX.X.
PYTHONPLATLIBDIR : override sys.platlibdir.
PYTHONCASEOK : ignore case in 'import' statements (Windows).
PYTHONUTF8: if set to 1, enable the UTF-8 mode.
PYTHONIOENCODING: Encoding[:errors] used for stdin/stdout/stderr.
PYTHONFAULTHANDLER: dump the Python traceback on fatal errors.
PYTHONHASHSEED: if this variable is set to 'random', a random value is used
to seed the hashes of str and bytes objects. It can also be set to an
integer in the range [0,4294967295] to get hash values with a
predictable seed.
PYTHONMALLOC: set the Python memory allocators and/or install debug hooks
on Python memory allocators. Use PYTHONMALLOC=debug to install debug
hooks.
PYTHONCOERCECLOCALE: if this variable is set to 0, it disables the locale
coercion behavior. Use PYTHONCOERCECLOCALE=warn to request display of
locale coercion and locale compatibility warnings on stderr.
PYTHONBREAKPOINT: if this variable is set to 0, it disables the default
debugger. It can be set to the callable of your debugger of choice.
PYTHONDEVMODE: enable the development mode.
PYTHONPYCACHEPREFIX: root directory for bytecode cache (pyc) files.
1.保留字
- 一 环境与编译器
保留字即关键字，我们不能把它们用作任何标识符名称。Python 的标准库提供了一个 keyword 模块，可以输出当前版本的所有关键字
>>> import keyword
>>> keyword.kwlist
['False', 'None', 'True', '__peg_parser__', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']
2.注释
- 一 环境与编译器
多行注释可以用多个 # 号，还有 ‘’’ 和 “”"
# 第一个注释
# 第二个注释
'''
第三注释
第四注释
'''
"""
第五注释
第六注释
"""
print ("这是咱的第一个python!")
3.缩进与行
- 一 环境与编译器
【缩紧】python最具特色的就是使用缩进来表示代码块，不需要使用大括号 {} 。缩进的空格数是可变的，但是同一个代码块的语句必须包含相同的缩进空格数。
if True:
print("Ture")
else:
print("False")
【行与换行】Python 通常是一行写完一条语句，但如果语句很长，我们可以使用反斜杠()来实现多行语句。在 [], {}, 或 () 中的多行语句，不需要使用反斜杠()
total = num1 + \
num2 + \
num3
week = ['星期一','星期二','星期三','星期四','星期五','星期六','星期天']
4.数字类型 Number
- 一 环境与编译器
数字的四种类型：整型 布尔 浮点数 复数
· int 证书类型. 1
·bool 布尔类型 True. True False
·float 浮点数. 1.23 3E-2
·complex 复数. 1+2j、 1.1+2.2j
4.字符串 String
- 一 环境与编译器
·python中单引号和双引号一样 word = ‘字符串’ word = “字符串”
·三引号（‘’’ 或者"“”) 指定一个多行字符串。注意开闭统一
·转译符号 ‘’
·反斜杠用来转移 r防止反斜杠转移 如：r’zhao Phor \n’ 的\n会显示
·按字面意义级联字符串，如"this " "is " "string"会被自动转换为this is string
·字符串拼接 + *运算符重复. 如：print(str * 2) # 输出字符串两次
·两种索引方式：0 左起➡️右 -1右起 ⬅️
·Python中的字符串不能改变。 解释如下 4.a
·Python 没有单独的字符类型，一个字符就是长度为 1 的字符串。
·字符串的截取的语法格式如下：变量[头下标:尾下标:步长]
