Sample Python Exam Problem Solutions

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Sample Python Exam Problem Solutions
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(Created page with "Problem: You are given a special type of List called mylist that has only a subset of functionality of Python lists. It provides the following methods: - mylist(): creates an e...")
 
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Problem: You are given a special type of List called mylist that has only a subset of functionality of Python lists. It provides the following methods:  
 
Problem: You are given a special type of List called mylist that has only a subset of functionality of Python lists. It provides the following methods:  
  
- mylist(): creates an empty mylist object
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* mylist(): creates an empty mylist object
- L.append(item): returns a new mylist that contains all the elements of L followed by item. Note that L is not modified.
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* L.append(item): returns a new mylist that contains all the elements of L followed by item. Note that L is not modified.
- L.pop(): returns a new mylist object containing all the elements of mylist L in the same order, except the last one. Note that L is not modified. L assumed to be non-empty.
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* L.pop(): returns a new mylist object containing all the elements of mylist L in the same order, except the last one. Note that L is not modified. L assumed to be non-empty.
- L.last(): returns the last element of L. L assumed to be non-empty.
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* L.last(): returns the last element of L. L assumed to be non-empty.
- L[index1:index2]: returns a new mylist that contains elements from position index1 to index2-1 (inclusive). Indexing starts at 0.
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* L[index1:index2]: returns a new mylist that contains elements from position index1 to index2-1 (inclusive). Indexing starts at 0.
- L.isempty(): returns True if L is empty object. Else it returns False.
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* L.isempty(): returns True if L is empty object. Else it returns False.
  
 
Some examples:  
 
Some examples:  

Revision as of 03:11, December 16, 2011

Problem: You are given a special type of List called mylist that has only a subset of functionality of Python lists. It provides the following methods:

Some examples:

mylist().append(4).append(3).last(): same as 3 mylist().append(4).append(3).pop(): same as mylist().append(4) mylist().append(4).isempty(): False mylist().append(4).pop().isempty(): True

Given the above mylist type, implement the following functions only using the above interface to mylist.

A. deletelasttwo(L): returns a mylist that contains all but the last two elements of L, in same sequence.

B. replacelast(L, item): returns a mylist that is same as L, except that the last value is replaced by item.

C. lookup(L, k): return the kth item in the mylist, where indexing starts at 0.

D. concat(L1, L2): returns a mylist that is a concatenation of L1 and L2.

E. insert_first(item, L): returns a mylist that contains item followed by items in L, in sequence.

F. len(L): returns the number of objects in mylist.

G; assign(L, index, val): Returns a new list identical to L, but in which the item at the index position in L is replaced by val.

All the methods are non-destructive, in the sense that the parameter L need not be modified.

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