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For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
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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