python 命令详解

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Python 是一种通用的高级编程语言。它的设计哲学强调代码的可读性，并且其语法允许程序员用更少的代码行来表达概念，而这种语言的语言表达少于 C 语言。Python 支持多种编程范例，包括面向对象，命令式和函数式 / 过程式。它具有动态键入系统，自动内存管理和全面的标准库。

python 命令安装：

-bash/zsh: python command not found

#Debian
apt-get install python-minimal

#Ubuntu
apt-get install python-minimal

#Alpine
apk add python

#Arch Linux
pacman -S python

#Kali Linux
apt-get install python-minimal

#CentOS
yum install python

#Fedora
dnf install python-minimal

#OS X
brew install python

#Raspbian
apt-get install python-minimal

#Docker
docker run cmd.cat/python python

python 命令补充说明：

Python 像其他动态语言一样，Python 通常用作脚本语言，但也可以编译成可执行程序。

Python 是由 Guido Van Rossum 创建的。Python 的开发始于 1989 年，并于 2008 年发布了 V3.0 版。

python 哲学：

Python 语言的核心理念包括以下戒律：

美丽胜于丑陋。
显式胜于隐式。
简单胜于复杂。
复杂胜于复杂。
可读性很重要。

python 命令选项：

-B
Don't write .py[co] bytecode files on import. See also PYTHONDONTWRITEBYTECODE.

-b
Issue warnings about str(bytes_instance), str(bytearray_instance) and comparing bytes/bytearray with str. (-bb issues errors rather than warnings)

-c command
Specify the command to execute (see next section). This terminates the option list (following options are passed as arguments to the command).

-d
Turn on parser debugging output (for advanced users only, depending on compilation options).

-E
Ignore environment variables like PYTHONPATH and PYTHONHOME that modify the behavior of the interpreter.

-h, -?, --help
Prints the usage for the interpreter executable and exits.

-i
When a script is passed as first argument or the -c option is used, enter interactive mode after executing the script or the command. It does not read the $PYTHONSTARTUP file. This can be useful to inspect global variables or a stack trace when a script raises an exception.

-I
Run Python in isolated mode. This also implies -E and -S. In isolated mode sys.path contains neither the script's directory nor the user's site-packages directory. All PYTHON* environment variables are ignored, too. Further restrictions may be imposed to prevent the user from injecting malicious code.

-m module-name
Searches sys.path for the named module and runs the corresponding .py file as a script.

-O
Turn on basic optimizations. This changes the filename extension for compiled (bytecode) files from .pyc to .pyo. Given twice, causes docstrings to be discarded.

-OO
Discard docstrings in addition to the -O optimizations.

-q
Do not print the version and Copyright messages. These messages are also suppressed in non-interactive mode.

-s
Don't add user site directory to sys.path.

-S
Disable the import of the module site and the site-dependent manipulations of sys.path that it entails. Also, disable these manipulations if site is explicitly imported later.

-u
Force the binary I/O layers of stdout and stderr to be unbuffered. stdin is always buffered. The text I/O layer is still line-buffered.

-v
Print a message each time a module is initialized, showing the place (filename or built-in module) from which it is loaded. When given twice, print a message for each file that is checked for when searching for a module. Also, provides information on module cleanup at exit.

-V, --version
Prints the Python version number of the executable and exits.

-W argument
Warning control. Python sometimes prints warning message to sys.stderr. A typical warning message has the following form: file:line: category: message. By default, each warning is printed once for each source line where it occurs. This option controls how often warnings are printed. Multiple -W options may be given; when a warning matches more than one option, the action for the last matching option is performed. Invalid -W options are ignored (a warning message is printed about invalid options when the first warning is issued). Warnings can also be controlled from within a Python program using the warnings module.

The simplest form of argument is one of the following action strings (or a unique abbreviation): ignore to ignore all warnings; default to explicitly request the default behavior (printing each warning once per source line); all to print a warning each time it occurs (this may generate many messages if a warning is triggered repeatedly for the same source line, such as inside a loop); module to print each warning only the first time it occurs in each module; once to print each warning only the first time it occurs in the program; or error to raise an exception instead of printing a warning message.

The full form of argument is action:message:category:module:line. Here, action is as explained above but only applies to messages that match the remaining fields. Empty fields match all values; trailing empty fields may be omitted. The message field matches the start of the warning message printed; this match is case-insensitive. The category field matches the warning category. This must be a class name; the match test whether the actual warning category of the message is a subclass of the specified warning category. The full class name must be given. The module field matches the (fully-qualified) module name; this match is case-sensitive. The line field matches the line number, where zero matches all line numbers and is thus equivalent to an omitted line number.

-X option
Set implementation specific option.

-x
Skip the first line of the source. This is intended to be a DOS-specific hack. (Warning: the line numbers in error messages will be off by one)