How do I format a string using a dictionary in python-3 x

Question

I am a big fan of using dictionaries to format strings  It helps me read the string format I am using as well as let me take advantage of existing dictionaries  For example   class MyClass      def   init   self           self title    Title   a   MyClass   print  The title is   title s    a   dict    path     path to a file  print  You put your file here    path s    locals     However I cannot figure out the python 3 x syntax for doing the same  or if that is even possible   I would like to do the following    Fails  KeyError  latitude  geopoint     latitude  41 123  longitude  71 091  print   latitude   longitude   format geopoint     Succeeds print   latitude   longitude   format latitude 41 123 longitude 71 091

User · Answer

The Python 2 syntax works in Python 3 as well    gt  gt  gt  class MyClass          def   init   self               self title    Title        gt  gt  gt  a   MyClass    gt  gt  gt  print  The title is   title s    a   dict    The title is Title  gt  gt  gt    gt  gt  gt  path     path to a file   gt  gt  gt  print  You put your file here    path s    locals    You put your file here   path to a file

User · Answer

As Python 3 0 and 3 1 are EOL ed and no one uses them  you can and should use str format map mapping   Python 3 2        Similar to str format   mapping   except that mapping is used directly and not copied to a dict  This is useful if for example mapping is a dict subclass    What this means is that you can use for example a defaultdict that would set  and return  a default value for keys that are missing    gt  gt  gt  from collections import defaultdict  gt  gt  gt  vals   defaultdict lambda    lt unset gt      bar    baz     gt  gt  gt   foo is  foo  and bar is  bar   format map vals   foo is  lt unset gt  and bar is baz    Even if the mapping provided is a dict  not a subclass  this would probably still be slightly faster   The difference is not big though  given   gt  gt  gt  d   dict foo  x   bar  y   baz  z     then    gt  gt  gt   foo is  foo   bar is  bar  and baz is  baz   format map d    is about 10 ns  2    faster than   gt  gt  gt   foo is  foo   bar is  bar  and baz is  baz   format   d    on my Python 3 4 3  The difference would probably be larger as more keys are in the dictionary  and     Note that the format language is much more flexible than that though  they can contain indexed expressions  attribute accesses and so on  so you can format a whole object  or 2 of them    gt  gt  gt  p1     latitude  41 123  longitude  71 091   gt  gt  gt  p2     latitude  56 456  longitude  23 456   gt  gt  gt    0 latitude    0 longitude   -  1 latitude    1 longitude    format p1  p2   41 123 71 091 - 56 456 23 456      Starting from 3 6 you can use the interpolated strings too    gt  gt  gt  f lat  p1  latitude    lng  p1  longitude      lat 41 123 lng 71 091    You just need to remember to use the other quote characters within the nested quotes  Another upside of this approach is that it is much faster than calling a formatting method

User · Answer

print   latitude   longitude   format   geopoint

User · Answer

Is this good for you   geopoint     latitude  41 123  longitude  71 091  print   latitude   longitude   format   geopoint

User · Answer

Since the question is specific to Python 3  here s using the new f-string syntax  available since Python 3 6    gt  gt  gt  geopoint     latitude  41 123  longitude  71 091   gt  gt  gt  print f  geopoint  latitude     geopoint  longitude      41 123 71 091   Note the outer single quotes and inner double quotes  you could also do it the other way around

User · Answer

To unpack a dictionary into keyword arguments  use     Also   new-style formatting supports referring to attributes of objects and items of mappings     0 latitude    0 longitude    format geopoint   The title is  0 title s  format a    the a from your first example

User · Answer

Most answers formatted only the values of the dict   If you want to also format the key into the string you can use dict items     geopoint     latitude  41 123  longitude  71 091  print         format  geopoint items       Output        latitude   41 123    longitude   71 091    If you want to format in an arbitry way  that is  not showing the key-values like tuples   from functools import reduce print     is    and    is     format  reduce  lambda x  y  x   y    list item  for item in geopoint items         Output      latitude is 41 123 and longitude is 71 091

User · Answer

geopoint     latitude  41 123  longitude  71 091     working examples  print f  geopoint  latitude     geopoint  longitude        from above answer print   geopoint latitude    geopoint longitude    format geopoint geopoint     alternate for format method   including dict name in string   print    latitude s   longitude s  geopoint    thanks  tcll

[python] How do I format a string using a dictionary in python-3.x?

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