Python-Perl cheatsheet

See also the Perl Phrasebook on wiki.python.org

what	Python	Perl	notes
null type	None	undef	not exactly identical
String concatenation	"py"+"thon"	"pe"."rl"
	if x == y	if ( $x == $y ) or if ( $x eq $y)	Perl requires parenthesis in a comparison (same for while). Perl uses different comparators for numbers and strings
Arrays
declare a list	[1,2,3]	(1,2,3)	note that arrays contain only scalars! (1,2, (3,4), 5) becomes (1,2,3,4,5)
array length	len(array)	$#array + 1	Python returns the length of array. Perl gives me the index of the last element. Also, the array value in a scalar context is (usually) its size.
	range(1,100)	(1..100)
create a list from whitespaced values	"fred barney wilma dino".split()	qw( fred barney wilma dino);	You can use separators others than parenthesis, e.g. qw ! fred barney wilma dino !
multiple assignment	fred, barney, dino = "flintstone", "rubble", None	($fred, $barney, $dino) = ("flintstone", "rubble", undef);
array concatenation	a+b	(@a, @b)	you can also mix like (@a, 3, @b, undef)
	array.append(item)	push @array, item;	See also Perl's unshift() for attaching to the front of array
	val = array.pop()	val = pop @array;	See also Perl's shift() for removing from the front of array
List iteration	for item in array	foreach $item (@array)	Note that $item is the real element of @array, so if you modify $item, you modify the array content
	list.reverse()	@list = reverse @list;	Python is in place, Perl is not. Same for sort.
Functions and subroutines
Subroutine/function declaration	def function(): ...	sub function { ... }
	return x	[last evaluated expression is return value]	Perl has no explicit return statement
	def function(arg1,arg2...)	sub function { ... $_[0] , $[1] ... }	Perl doesn't have explicit arguments; args are stored in the @_ default array.
	def function(arg1,arg2...)	sub function { my($arg1, $arg2) = @_; }	You can name arguments by declaring them using the @_ default array