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9.6. List methods

Python provides methods that operate on lists. For example, append adds a new element to the end of a list:

t = ['a', 'b', 'c'] t.append('d') print(t)

Q-2: What is printed by the following statements?

alist = [4, 2, 8, 6, 5]
alist.append(True)
alist.append(False)
print(alist)

• [4, 2, 8, 6, 5, False, True]
• True was added first, then False was added last.
• [4, 2, 8, 6, 5, True, False]
• Yes, each item is added to the end of the list.
• [True, False, 4, 2, 8, 6, 5]
• append adds at the end, not the beginning.

extend takes a list as an argument and appends all of the elements:

t1 = ['a', 'b', 'c'] t2 = ['d', 'e'] t1.extend(t2) print(t1)

This example leaves t2 unmodified.

sort arranges the elements of the list from low to high:

t = ['d', 'c', 'e', 'b', 'a'] t.sort() print(t)

Q-5: True or False? The sort method alphabetizes lists.

• True
• While this may be true if the values are letter characters, sort can be used on lists with different elements, too.
• False
• The sort method puts elements in order of low to high, this can be true for letters, numbers, or whatever the elements of the list are.

Most list methods are void; they modify the list and return None. If you accidentally write t = t.sort(), you will be disappointed with the result.

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