Python, Ruby, Perl: Basic String Operations

Xah Lee, 2005-01-10, 2012-12-16

Python

Substring

Substring extraction is done by appending [‹begin index›:‹end index›].

#-*- coding: utf-8 -*-
# python

aa = "01234567"
print aa[2:4] # prints “23”. Does not include the end.

# negative index counts from end, starting with -1
bb = "this"
print bb[0:-2] # prints “th”

# when first index is omitted, default to 0.
# when second index is omitted, default to -1.
cc = "that"
print cc[:] # prints “that”

String Length

Length of the string is len().

#-*- coding: utf-8 -*-
# python

a="this"
print len(a) # 4

String Join ＆ Repetition

Strings can be joined by a plus sign +.

#-*- coding: utf-8 -*-
# python

print "this" + " that"

String can be repeated using *.

#-*- coding: utf-8 -*-
# python

print "this" * 2

• http://docs.python.org/library/stdtypes.html#typesseq
• http://docs.python.org/library/stdtypes.html#string-methods

Ruby

Substring

Substring extraction is done by appending a bracket [‹index›,‹count›].

#-*- coding: utf-8 -*-
# ruby

# substring
aa = "01234567"
p aa[0,2]                   # prints “01”. Start with index, then count of chars.

# negative index counts from end. -1 is last char.
p aa[-2,2]                   # prints “67”.

String Length

Length of the string is .length method.

# -*- coding: utf-8 -*-
# ruby

a="this"
p a.length                      # 4

String Join ＆ Repetition

Strings can be joined by a plus sign +.

# -*- coding: utf-8 -*-
# ruby

p "this" + " that"              # "this that"

String can be repeated using *.

# -*- coding: utf-8 -*-
# ruby

print "this" * 2                # thisthis

Perl

Substring

String extraction is done with substr(). The form is: substr($myString, offset index, number of characters to extract).

# -*- coding: utf-8 -*-
# perl

# substring. 2nd arg  is begin index, 3rd arg is count
print substr('012345', 2, 2); # prints 23

String Length

Length of string is length().

print length('abc');

String Join ＆ Repetition

In Perl, string join is done with a dot.

$astr= "under" . "stand";

String repetition is done with the operator x.

print 'abc' x 2;

• perldoc -f substr
• perldoc perlop