Page 353 - Computer Science V2.0 Class 11

Next, let us consider a more interesting piece of code:
01 s = 'abcdefghij' #Initial s
02 print('id(s):', id(s), 's:', s)
03 for ch in s:
04 s = s + ch
05 print('id(s):', id(s), 's:', s)
06 print('id(s):', id(s), 's:', s) # Final s
The above code yielded the following output on execution:

id(s): 1631127023152 s: abcdefghij
id(s): 1631126713008 s: abcdefghija
id(s): 1631126713008 s: abcdefghijab
id(s): 1631126713008 s: abcdefghijabc

id(s): 1631126713008 s: abcdefghijabcd
id(s): 1631126713008 s: abcdefghijabcde
id(s): 1631127097456 s: abcdefghijabcdef

id(s): 1631127097456 s: abcdefghijabcdefg
id(s): 1631127097456 s: abcdefghijabcdefgh
id(s): 1631127097456 s: abcdefghijabcdefghi
id(s): 1631127097456 s: abcdefghijabcdefghij
id(s): 1631127097456 s: abcdefghijabcdefghij
Note that even though the variable s finally denotes the string abcdefghijabcdefghij, the control exits the
for-loop on processing the characters of the initial string s: abcdefghij. Also, note that when a string object has
outlived its purpose, Python may not create a new object id for another string object. Thus, the strings, 'abcdefghij',
'abcdefghijab', 'abcdefghijabc', 'abcdefghijabcd', and 'abcdefghijabcde' have the same
object id. However, it is not a general rule, and the strings 'abcdefghijabcde' and 'abcdefghijabcdef'
have different object ids. As a general rule, we should avoid such obfuscated codes.

Never modify the value of a control variable inside a for-loop.

12.1.9 Transforming Numerical Values to Strings

A numerical value may be transformed into a string using the str() function. For example,

>>> 'I want' + str(2) + 'cups of ice cream.'
'I want 2 cups of ice cream.'

Membership operator in: Examine the membership of a particular character or a substring in the given string using
the membership operator in.
str(): To transform a data object to a string

12.2 String Slices

Often, we are interested in extracting/accessing more than one character, i.e. a subsequence of characters from the
string. For example, we may be looking for the last name of an employee, or we may be interested in a name beginning
with Abhishek. A subsequence of characters in a string is called a slice. A slice is marked by specifying the start and
finish indices using the notation: <start>:<finish>.

Strings 339