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Reading command line parameters in Python

The sys module in Python gives you access to operating system parameters such as the command line interface, via an ordered collection (I think a list, may be a tuple) called argv. Although many / most users these days don't use the command line directly, it's often used internally between programs in a batch file or command / shell script, in regular time jobs, between web servers and programs, and so on - so you may need to use it more than you expect.

For this week's course I've written a very shorr example [here] to show this in use.

  from sys import *
  for thing in argv:
    print "I gotta", thing


Note that the first value that comes back is the name of your program, and the following items are individual paramaters as processed by the command line handler. Thus ...

Just the command - a single parameter:

  trainee@kingston:~/elen$ avx
  I gotta ./avx


The command with some space separated parameters (note that "-l" looks like an option but is really just a parameter):

  trainee@kingston:~/elen$ avx -l 15.0 metres
  I gotta ./avx
  I gotta -l
  I gotta 15.0
  I gotta metres


Use of command line special characters will be reflected in what your python program gets - here using quotes to make a single string for you:

  trainee@kingston:~/elen$ avx "Single String"
  I gotta ./avx
  I gotta Single String


... and here piping what you output from your program into another command; you don't see this is happening from argv:

  trainee@kingston:~/elen$ avx "Single String" | cat
  I gotta ./avx
  I gotta Single String


(written 2015-02-23, updated 2015-02-24)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
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  [4697] Month, Day, Year number to day of week and month names in Python - English and Swedish - (2016-06-23)
  [4696] Programming with random numbers - yet re-using the same values for testing - (2016-06-22)
  [4452] Binary data handling - Python and Perl - (2015-03-09)
  [4086] Cacheing class for Python - using a local SQLite database as a key/value store - (2013-05-14)
  [4085] JSON from Python - first principles, easy example - (2013-05-13)
  [3479] Practical Extraction and Reporting - using Python and Extreme Programming - (2011-10-14)
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  [2931] Syncronise - software, trains, and buses. Please! - (2010-08-22)
  [2890] Dates and times in Python - (2010-07-27)
  [2506] Good example of recursion in Python - analyse an RSS feed - (2009-11-18)
  [2020] Learning Python - many new example programs - (2009-01-31)

Y105 - Python - Functions, Modules and Packages
  [4724] From and Import in Python - where is the module loaded from? - (2016-11-06)
  [4722] Embedding more complex code into a named block - (2016-11-04)
  [4719] Nesting decorators - (2016-11-02)
  [4662] Recursion in Python - the classic example - (2016-03-07)
  [4645] What are callbacks? Why use them? An example in Python - (2016-02-11)
  [4448] What is the difference between a function and a method? - (2015-03-04)
  [4410] A good example of recursion - a real use in Python - (2015-02-01)
  [4407] Python - even named code blocks are objects - (2015-01-28)
  [4361] Multiple yields and no loops in a Python generator? - (2014-12-22)
  [4212] Python functions - an introduction to how they work - (2013-11-16)
  [4161] Python varables - checking existance, and call by name or by value? - (2013-08-27)
  [4029] Exception, Lambda, Generator, Slice, Dict - examples in one Python program - (2013-03-04)
  [3945] vargs in Python - how to call a method with unknown number of parameters - (2012-12-06)
  [3931] Optional positional and named parameters in Python - (2012-11-23)
  [3885] Default local - a good choice by the author of Python - (2012-10-08)
  [3852] Static variables in Python? - (2012-08-29)
  [3766] Python timing - when to use a list, and when to use a generator - (2012-06-16)
  [3695] Functions are first class variables in Lua and Python - (2012-04-13)
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  [3474] Python Packages - groupings of modules. An introduction - (2011-10-11)
  [3472] Static variables in functions - and better ways using objects - (2011-10-10)
  [3464] Passing optional and named parameters to python methods - (2011-10-04)
  [3459] Catching the fishes first? - (2011-09-27)
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  [340] Code and code maintainance efficiency - (2005-06-08)
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  [303] Lambdas in Python - (2005-05-06)
  [294] Python generator functions, lambdas, and iterators - (2005-04-28)
  [105] Distance Learning - (2004-10-31)
  [96] Variable Scope - (2004-10-22)


Back to
A first graph with Matplotlib in Python
Previous and next
or
Horse's mouth home
Forward to
Mutable v Immuatble objects in Python, and the implication
Some other Articles
Graphing presentations in Python - huge data, numpy and matplotlib
Elements of an exception in Python - try, except, else, finally
Seventh stay away this year - and it's still only February!
Mutable v Immuatble objects in Python, and the implication
Reading command line parameters in Python
A first graph with Matplotlib in Python
Json is the new marshall, pickle and cPickle / Python
Loving programming in Python - and ready to teach YOU how
Adding a PHP build option, rotating an image based on camera data, and a new look at thumbnails in PHP
Accessing a MySQL database from Python with mysql.connector
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