If you erect a fence of 10 panels, you'll need 11 fenceposts to hold it up. And if you write a program that joins together 10 elements on a line, you'll only need 9 separators between them - this is known as the "fencepost problem".

If you write a simple program loop to output each element from a list followed by a separator, you'll end with a spurious separator on the end of the line. Here's what I mean (in Python).

posts = ["apple","banana","cherry"]

panel = "and"

for place in posts:

   print place,panel,

print

which gives the result

apple and banana and cherry and

It would be possible - but long winded - to print out the connecting panel only for the second and subsequent posts:

posts = ["apple","banana","cherry"]

panel = "and"

i = 0

for place in posts:

   if i: print panel,

   i += 1

   print place,

print

but surely there's a better way?? Yes - there is.


In Python, the join method lets me connect a list of strings using another string as the glue between them. My example becomes:

posts = ["kiwi","orange","pineapple"]

panel = " with "

salad = panel.join(posts)

print salad

which gives the result

kiwi with orange with pineapple


Link - full source code


In Perl, the join function performs the same task:

@salad = ("Cherry","Damson",Fig");

print (join(" and ",@salad));

With PHP, the function you'll use is implode:

$salad = array("tangerine","pear","grape");

$fsal = implode(" and ",$salad);

(written 2006-01-10 03:03:12)

 Y108 - Python - String Handling
H107 - String Handling in PHP
P208 - Perl - Lists

Back to ''I don't know'' is sometimes a good answer

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Forward to Python's Generator functions

Open Source training from Well House Consultants
Merging pictures using PHP and GD
Smoke and mirrors
Python's Generator functions
The fencepost problem
''I don't know'' is sometimes a good answer
Converting between acres and hectares
A new sign
Colour doesn't have to mean colourful
Hotel novelties
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