For 2023 - 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 Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own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)) |
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)
Some other Articles
Annual review of Melksham Matters for Chamber of Commerce AGMRuby training, half a world awayThe end, or the start?Buses - how did we get into the situation we are in?Sorting a dict in PythonWiltshire Supported Bus consultation - final few daysSpring at Well House ManorChippenham to Salisbury by public transport - what we have and what we could haveMallory Place bus stop - services to BathEasy data to object mapping (csv and Python)
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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.
Link to Ezine home page (for reading).
Link to Blogging home page (to add comments).
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