Page 291 - Computer Science Class 11 Without Functions
P. 291
A list assignment does not create a new copy of the list. Instead, on the execution of the assignment statement, the
variable on the left-hand side of the assignment statement refers to the list on the right-hand side of the assignment
statement; for example,
>>> colors
['red', 'green', 'blue',]
>>> colorsRef = colors
>>> id(colors)
1777056884928
>>> id(colorsRef)
1777056884928
Note that the variables colors and colorsRef refer to the same list of objects having the id: 1777056884928.
Variables that refer to the same object are called aliases of each other. Thus, each of the variables colors and
colorsRef is an alias of the other.
As the variables colors and colorsRef refer to the same list, changes made to the list, named colorsRef, are
reflected in the list, as illustrated below:
Fig 12.1: As the names colorsRef and colors are aliases of each other, either of these names may be used to modify
the list.
On execution of line 3 in Fig 12.1, the value at index 1 in the list colorsRef is updated to 'yellow'. The modification
gets reflected again, when we print the list colors (line 4) as each of the variables colorsRef and colors refers
to the list object (see Fig 12.1) .
12.3 Traversing a List
We can traverse a list by iterating over each element of the list using a for loop or while loop.
12.3.1 Using for loop
>>> lst = [1, 2, 3, 4, 5]
... for element in lst: # using for loop
... print(element,end=' ')
Output:
1 2 3 4 5
Lists and Tuples 289

