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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.
Sorting a dict in Python

* You cannot sort a dict
* If you sort a list of strings that are digits, you don't get a numeric sort by default

Solutions

* Sort a list of keys
* Specifiy a sort lambda (Python 2 comparator, Python 3 key function) for that list

Example code:

  stuff = {'9': 36, '10': 26, '8': 25, '6': 2}
  
  print "Sorting in NUMERIC order ----------------------- "
  names = stuff.keys()
  names.sort(lambda x,y: int(x)-int(y))
  
  print "Output in NUMERIC order ----------------------- "
  for name in names:
    print name,stuff[name]


Following code fills in the gaps for missing keys:

  print "Filling the 'gaps' ---------------------------- "
  for want in range(int(names[0]),int(names[-1])+1):
    stuff[str(want)] = stuff.get(str(want),0)
  
  print "Output in NUMERIC order ----------------------- "
  for name in range(int(names[0]),int(names[-1])+1):
    print name,stuff[str(name)]


Running that:

  WomanWithCat:apr16 grahamellis$ python od
  Sorting in NUMERIC order -----------------------
  Output in NUMERIC order -----------------------
  6 2
  8 25
  9 36
  10 26
  Filling the 'gaps' ----------------------------
  Output in NUMERIC order -----------------------
  6 2
  7 0
  8 25
  9 36
  10 26
  WomanWithCat:apr16 grahamellis$


Complete source for Python 2 - [here] or for Python 3 [here].

As an alterative, take a look at the OrderedDict class in the collections module.
(written 2016-04-01, updated 2016-04-02)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
Y107 - Python - Dictionaries
  [103] Can't resist writing about Python - (2004-10-29)
  [955] Python collections - mutable and imutable - (2006-11-29)
  [1144] Python dictionary for quick look ups - (2007-04-12)
  [1145] Using a list of keys and a list of values to make a dictionary in Python - zip - (2007-04-13)
  [2368] Python - fresh examples of all the fundamentals - (2009-08-20)
  [2915] Looking up a value by key - associative arrays / Hashes / Dictionaries - (2010-08-11)
  [2986] Python dictionaries - reaching to new uses - (2010-10-05)
  [2994] Python - some common questions answered in code examples - (2010-10-10)
  [3464] Passing optional and named parameters to python methods - (2011-10-04)
  [3488] Python sets and frozensets - what are they? - (2011-10-20)
  [3554] Learning more about our web site - and learning how to learn about yours - (2011-12-17)
  [3555] Football league tables - under old and new point system. Python program. - (2011-12-18)
  [3662] Finding all the unique lines in a file, using Python or Perl - (2012-03-20)
  [3934] Multiple identical keys in a Python dict - yes, you can! - (2012-11-24)
  [4027] Collections in Python - list tuple dict and string. - (2013-03-04)
  [4029] Exception, Lambda, Generator, Slice, Dict - examples in one Python program - (2013-03-04)
  [4409] Setting up and using a dict in Python - simple first example - (2015-01-30)
  [4469] Sorting in Python 3 - and how it differs from Python 2 sorting - (2015-04-20)
  [4661] Unique word locator - Python dict example - (2016-03-06)


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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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