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The Interpolation Operator - Python

As the students used to say to Mr. Kotter: "Welcome back, welcome back, welcome back." In our previous article we talked some more about how to manipulate strings in Python, leaving off with indexing and slicing. Here, we will pick up again with slicing, using it to “change” the contents of a string.

TABLE OF CONTENTS:
  1. Python Strings: Spinning Yarns
  2. The Interpolation Operator
  3. Changing Strings with Methods
  4. Dealing with Multiple Words
By: James Payne
Rating: starstarstarstarstar / 3
February 11, 2008

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When we wish to specify what happens to a value when we insert it into a string, we can do so using the interpolation operator(%). We can use this to insert data inside of a string, determine how many digits are displayed next to a decimal, determine how much space to allow for the data (known as the minimum field width), and more.

Here is a list of possible formatting code you can insert after the interpolation operator(%):


  • %c - used for a single character

  • %d and %i - used for signed integer decimals

  • %f and %F - used for floating point decimals

  • %r - represents the data

  • %% - used as an escape character for the percentage symbol

To insert a single character into a string, we can do so, as described above, using %c. Here it is in code:

missing='F'

print 'Which character is missing from the following sequence?'

print 'A B C D E %c G H I J K L M N O P Q R S T U V W X Y Z' %missing

When the code prints, it replaces the code %c with the value in our variable, missing, which in this instance is 'F'. Here is the result:

  Which character is missing from the following sequence?

  A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

If we wanted to insert an entire word or sentence, or string, we could do that as well by using %s:


hawtness='James Payne'

print "And the winner of this years Uber Hawtness award goes to....*drumroll*"

print "The magnanimous, heroic, super-strong, giant-brained, whicka whicka %s ! Whoeee!" %hawtness

In this code, the program sees the %s and replaces it with the value stored in the variable hawtness. The result is:

  And the winner of this years Uber Hawtness award goes to....*drumroll*

  The magnanimous, heroic, super-strong, giant-brained, whicka whicka James   Payne ! Whoeee!

We can, of course, also insert multiple words into our string, using the following method:


hawtness='James Payne'

gf='Angelina Jolie'

name='Jamesalina'

print 'Here comes the hot new hollywood couple now.'

print '%s in an Armani suit, looking dashing and %s in a birthday suit as %s demands it!' % (hawtness, gf, hawtness)

print 'As a couple we dub thee...%s' %name

This displays:

  Here comes the hot new hollywood couple now.

  James Payne in an Armani suit, looking dashing and Angelina Jolie in a birthday suit as James Payne demands it!

  As a couple we dub thee...Jamesalina

The technique works for characters as well:


first='a'

second='b'

third='c'

fourth='d'

fifth='e'

sixth='f'

seventh='g'

eighth='h'

print 'Here are the first eight letters of the alphabet...'

print '%c %c %c %c %c %c %c %c' % (first, second, third, fourth, fifth, sixth, seventh, eighth)

And the result:

  Here are the first eight letters of the alphabet...

  a b c d e f g h



 
 
>>> More Python Articles          >>> More By James Payne
 

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