Using Python command line

Recently I had a task to write a command file for Windows that run a simple Python commands via python –c command. The manual says that command may contain multiple statements separated by newlines. Unfortunately, Windows console doesn’t allow it (and Ctrl-T trick doesn’t help) so I had to find a workaround. The intuition and language reference helped me to find out that the simple statements can be separated by semicolons like in C/C++ (however, these languages allow to separate all the commands, not
the only simple ones).

Let me give an example. Imagine that accidentally I want to know the error message corresponding to the error code 9. Of course, I can read manuals and documentation, but there is a more simple way:

$ python -c "import os;print os.strerror(9)"
Bad file descriptor

But this "trick" works only with simple statements. It is not allowed to mix simple and compound statements, so the following command will not work: python -c "import os;for i in range(42):print i,os.strerror(i)". The only way to make it workable – put compound statement on the upper level (identical imports doesn't matter, the real import will be executed only once):

$ python -c "for i in range(43):import os;print i,os.strerror(i)"
0 No error
1 Operation not permitted
2 No such file or directory
3 No such process
4 Interrupted function call
5 Input/output error
6 No such device or address
7 Arg list too long
8 Exec format error
9 Bad file descriptor
10 No child processes
11 Resource temporarily unavailable
12 Not enough space
13 Permission denied
14 Bad address
15 Unknown error
16 Resource device
17 File exists
18 Improper link
19 No such device
20 Not a directory
21 Is a directory
22 Invalid argument
23 Too many open files in system
24 Too many open files
25 Inappropriate I/O control operation
26 Unknown error
27 File too large
28 No space left on device
29 Invalid seek
30 Read-only file system
31 Too many links
32 Broken pipe
33 Domain error
34 Result too large
35 Unknown error
36 Resource deadlock avoided
37 Unknown error
38 Filename too long
39 No locks available
40 Function not implemented
41 Directory not empty
42 Illegal byte sequence 

Also I want to notice one more feature of Python command line – executing modules content. Python contains many useful modules and some of them are more useful than
someone can think – they can be executed. For example, SimpleHTTPServer allows you to share your current directory information and files via HTTP protocol:

$ python -m SimpleHTTPServer
Serving HTTP on 0.0.0.0 port 8000 ... 

I’ve gathered information about executable modules and want to share it with you:

Command	Functionality
python -m site	Print some useful information (sys.path, USER_BASE, USER_SITE)
python -m StringIO	Read information about the file (default: /etc/passwd)
python -m calendar	Show the console calendar
python -m zipfile	Zip/unzip analogue
python -m platform	Print the platform information
python -m mailcap	Show and execute MIME types handlers
python -m binhex	Convert the binary file to hex
python -m sgmllib	Parse the html file
python -m htmllib	Show the html file in the text mode
python -m webbrowser	Start the default web browser for the required URL
python -m urllib	Print the content of the remote site
python -m ftplib	Simple FTP client
python -m poplib	Print information about the remote mailbox
python -m smtpd	RFC 2821 SMTP proxy
python -m telnetlib	Simple telnet client
python -m SimpleHTTPServer	Simple HTTP server
python -m CGIHTTPServer	CGI-savvy HTTP server
python -m aifc	Print information about the .aiff file
python -m sndhdr	Print information about sound files
python -m locale	Print locale information
python -m shlex	Split the file to tokens
python -m pydoc	Python documentation tool
python -m doctest	Doctest runner
python -m unittest	Unittest runner
python -m pdb	Python debugger
python -m timeit	Tool for measuring execution time of small code snippets
python -m trace	Trace Python program or function execution
python -m code	Python interpreter emulator
python -m tokenize	Split the file to tokens with detailed information
python -m pyclbr	Describe Python module classes and methods
python -m compileall	Compile all .py files to .pyc (.pyo) files
python -m filecmp	Compare two directory
python -m gzip	Gzip/gunzip analogue
python -m base64	RFC 3548: Base16, Base32, Base64 data encoder
python -m quopri	Convert to/from quoted-printable transport encoding as per RFC 1521
python -m cProfile	Profile Python code via 'lsprof' profiler
python -m profile	Profile Python code
python -m uu	Implement UUencode and UUdecode functions
python -m dis	Disassemble of Python byte code into mnemonics
python -m formatter	Generic output formatter

Most useful modules will be described in my next article. Enjoy!