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For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
Python - comparison of old and new string formatters

The % operator in Python when applied to a string object formats the object to the right using the format specifier to the left, using the same notations as the C function sprintf.

For example:
  >>> j = 1.0 / 7.0
  >>> print j
  0.142857142857
  >>> print "j has a value %.2f !!" % j
  j has a value 0.14 !!
  >>>


That's good and effective, but lacks some of the flexibility that's desirable, and could be provided these days.

So - from Python 2.6 a format method has been provided on string objects,
using a {} notation with an extended capability in place of %:
  >>> print "j has a value {0:.2f} !!".format(j)
  j has a value 0.14 !!
  >>>


The "0" in the placeholder indicates that this element is to be filled in using element No. 0 from the tuple that's passed in to the format method. So you're allowed to re-use paramaters, specify them in different orders, ignore values if you wish (e.g. a changing format string) and you can even use named values from a dict.

  >>> filler = {"person":"porridge", "wall":"Polyfilla"}
  >>> print "Fill youself with {person} and your home with {wall}".format(**filler)
  Fill youself with porridge and your home with Polyfilla
  >>>


In Python 2.7, you can also leave out the position specifier - if you don't give a name or a number, it defaults to first value filled to first set of {}, second value to second set, etc.

An example (showing old and new styles for the same data) - [here] from last week's Python course. And there's a further example (updated, from the notes) [here].
(written 2014-12-22)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
Y108 - Python - String Handling
  [324] The backtick operator in Python and Perl - (2005-05-25)
  [463] Splitting the difference - (2005-10-13)
  [496] Python printf - (2005-11-15)
  [560] The fencepost problem - (2006-01-10)
  [773] Breaking bread - (2006-06-22)
  [903] Pieces of Python - (2006-10-23)
  [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25)
  [954] Splitting Pythons in Bradford - (2006-11-29)
  [970] String duplication - x in Perl, * in Python and Ruby - (2006-12-07)
  [1110] Python - two different splits - (2007-03-15)
  [1195] Regular Express Primer - (2007-05-20)
  [1517] Python - formatting objects - (2008-01-24)
  [1608] Underlining in Perl and Python - the x and * operator in use - (2008-04-12)
  [1876] Python Regular Expressions - (2008-11-08)
  [2284] Strings as collections in Python - (2009-07-12)
  [2406] Pound Sign in Python Program - (2009-09-15)
  [2692] Flexible search and replace in Python - (2010-03-25)
  [2721] Regular Expressions in Python - (2010-04-14)
  [2765] Running operating system commands from your Python program - (2010-05-14)
  [2780] Formatted Printing in Python - (2010-05-25)
  [2814] Python - splitting and joining strings - (2010-06-16)
  [3090] Matching to a string - what if it matches in many possible ways? - (2010-12-17)
  [3218] Matching a license plate or product code - Regular Expressions - (2011-03-28)
  [3349] Formatting output in Python through str.format - (2011-07-07)
  [3468] Python string formatting - the move from % to str.format - (2011-10-08)
  [3469] Teaching dilemma - old tricks and techniques, or recent enhancements? - (2011-10-08)
  [3796] Backquote, backtic, str and repr in Python - conversion object to string - (2012-07-05)
  [3886] Formatting output - why we need to, and first Python example - (2012-10-09)
  [4027] Collections in Python - list tuple dict and string. - (2013-03-04)
  [4152] Why are bus fares so high? - (2013-08-18)
  [4213] Formatting options in Python - (2013-11-16)
  [4307] Identifying and clearing denial of service attacks on your Apache server - (2014-09-27)
  [4593] Command line parameter handling in Python via the argparse module - (2015-12-08)
  [4595] Python formatting update - including named completions - (2015-12-10)
  [4659] Prining a pound sign from Python AND running from the command line at the same time - (2016-03-03)


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Some other Articles
Christmas day in Melksham
A quiet evening in Melksham - awaiting Santa
What a difference a year makes
Multiple yields and no loops in a Python generator?
Python - comparison of old and new string formatters
How to avoid too many recalculations within an object
A brilliant finish to 2014 training and business guests, and a look to 2015
Seeing Christmas Coming to Melksham
Object factories in C++, Python, PHP and Perl
C++ in 2 days
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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