Data structures

Data Structures
Vikram Neerugatti
Sri Venkateswara College of Engineering

Content
• Lists
• Operations
• Slicing
• Methods
• Tuples
• Dictionaries
• Sets
• Comparisons
27-03-2020 Vikram Neerugatti, Assistant Professor, SVCET, CHITTOOR. 2

Lists
• Lists is collection of elements.
• Elements are changeable and duplicates are allowed.
• Example: A=[1,2,3]
• Example 1
• A=[1,2,3] # only numerical in list
• print(A)
• Example 2
• B=["a",3,[2,3]] #list within the list and alphabets
• print(B)
• Elements can be list and other than numerical also
• x=[2,2,3] #duplicates
• print(x)

Lists
• To access the elements in list- indexing is used
• List index range is 0 to n-1
• x=[2,2,3]
• print(x) #nani
• Positive indexing
• c=x[2] # 2 is the index
• print(c)
• Négative indexing
• d=x[-1]
• print(d)

lists
• Can access the elements by range
• x=[2,2,3]
• print(x) #nani
• c=x[2]
• print(c)
• d=x[0:3]
• print(d)
• Négative range
• d=x[-3:-1]
• print(d)

lists
• Len()
• Append()
• Insert()
• Remove()
• Pop()
• Del
• Clear()
• Copy()

Tuples
• A tuple is a collection which is ordered and unchangeable. In Python tuples are written
with round brackets.
• Example: a=(3,5,6,7)
• To change the values in tuple, it should be converted into list by using list function and
can be changed.
• Remaining all the operations and slicing can be done as the list.
• It has the methods shown in next slide.

Tuples
• Example
• a=(4,5,4,4,6,7)
• print(a)
• b=list(a)
• print(b)
• print(a[2:4])
• c=a.count(4)
• print(c)
• f=a.index(6)
• print(f)

Sets
• A set is a collection which is unordered and unindexed. In Python sets are written with curly brackets.
• You cannot access items in a set by referring to an index, since sets are unordered the items has no index.
• Add()-to add an item
• Update()-to add multiple items
• Remove() or discard() or pop()-to remove an item from sets
• Clear()-empties the sets
• del-deletes the list

Dictionaries
• A dictionary is a collection which is unordered, changeable and indexed.
• In Python dictionaries are written with curly brackets, and they have keys and values.
• Example
• thisdict = {
"brand": "Ford",
"model": "Mustang",
"year": 1964
}
print(thisdict)

Dictionaries
• You can access the items of a dictionary by referring to its key name, inside square brackets:
• x = thisdict["model"]
• Get()-can access the valur by using the key
• Pop()-deletes by key
• Popitem()- deletes last inserted element
• Del-removes the items
• Values(),items(),keys(), clear(), copy()

Comparisons

Summary
• Lists
• Operations
• Slicing
• Methods
• Tuples
• Dictionaries
• Sets
• Comparisons

Data structures

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