Python : Data Types

Comments
Single Line Comments
● Starts with # symbol
● Comments are non-executable statements
1 #To find sum of two numbers
2 a = 10 #Store 10 into variable 'a'

Comments
Multi Line Comments
● Version-1
● Version-2
● Version-3
1 #To find sum of two numbers
2 #This is multi-line comments
3 #One more commented line
4 """
5 This is first line
6 This second line
7 Finally comes third
8 """
4 '''
5 This is first line
6 This second line
7 Finally comes third
8 '''

Docstrings
Multi Line Comments
● Python supports only single line commenting
● Strings enclosed within ''' … ''' or """ … """, if not assigned to any variable, they are removed from
memory by the GC
● Also called as Documentation Strings OR docstrings
● Useful to create API file
Command to Create the html file
-------------------------------
py -m pydoc -w 1_Docstrings
-m: Module
-w: To create the html file

Data-Types
None Type
● None data-type represents an object that does not contain any value
● In Java, it is called as NULL Object
● In Python, it is called as NONE Object
● In boolean expression, NONE data-type represents ‘False’
● Example:
○ a = “”

Data-Types
Numeric Type
● int
○ No limit for the size of an int datatype
○ Can store very large numbers conveniently
○ Only limited by the memory of the system
○ Example:
■ a = 20

Data-Types
Numeric Type
● float
○ Example-1:
■ A = 56.78
○ Example-2:
■ B = 22.55e3 ⇔ B = 22.55 x 10^3

Data-Types
Numeric Type
● Complex
○ Written in the form a + bj OR a + bJ
○ a and b may be ints or floats
○ Example:
■ c = 1 + 5j
■ c = -1 - 4.4j

Representation
Binary, Octal, Hexadecimal
● Binary
○ Prefixed with 0b OR 0B
■ 0b11001100
■ 0B10101100
● Octal
○ Prefixed with 0o OR 0O
■ 0o134
■ 0O345
● Hexadecimal
○ Prefixed with 0x OR 0X
■ 0xAB
■ 0Xab

Conversion
Explicit
● Coercion / type conversions
○ Example-1:
○ Example-2:
x = 15.56
int(x) #Will convert into int and display 15
x = 15
float(x) #Will convert into float and display 15.0

Conversion
Explicit
○ Example-3:
○ Example-4:
a = 15.56
complex(a) #Will convert into complex and display (15.56 + 0j)
a = 15
b = 3
complex(a, b) #Will convert into complex and display (15 + 3j)

Conversion
Explicit
○ Example-5: To convert string into integer
○ Syntax: int(string, base)
○ Other functions are
■ bin(): To convert int to binary
■ oct(): To convert oct to binary
■ hex(): To convert hex to binary
str = “1c2”
n = int(str, 16)
print(n)

bool Data-Type
● Two bool values
○ True: Internally represented as 1
○ False: Internally represented as 0
● Blank string “” also represented as False
● Example-1:
a = 10
b = 20
if ( a < b):
print(“Hello”)

bool Data-Type
● Example-2:
● Example-3:
a = 10 > 5
print(a) #Prints True
a = 5 > 10
print(a) #Prints False
print(True + True) #Prints 2
print(True + False) #Prints 1

Sequences
str
● str represents the string data-type
● Example-1:
● Example-2:
3 str = "Welcome to Python"
4 print(str)
5
6 str = 'Welcome to Python'
7 print(str)
3 str = """
4 Welcome to Python
5 I am very big
6 """
7 print(str)
8
9 str = '''
10 Welcome to Python
11 I am very big
12 '''
13 print(str)

Sequences
str
● Example-3:
● Example-4:
3 str = "This is 'core' Python"
4 print(str)
5
6 str = 'This is "core" Python'
7 print(str)
3 s = "Welcome to Python"
4
5 #Print the whole string
6 print(s)
7
8 #Print the character indexed @ 2
9 print(s[2])
10
11 #Print range of characters
12 print(s[2:5]) #Prints 2nd to 4th character
13
14 #Print from given index to end
15 print(s[5: ])
16
17 #Prints first character from end(Negative indexing)
18 print(s[-1])

Sequences
str
● Example-5:
3 s = "Emertxe"
4
5 print(s * 3)

Sequences
bytes
● bytes represents a group of byte numbers
● A byte is any positive number between 0 and 255(Inclusive)
● Example-1:
3 #Create the list of byte type array
4 items = [10, 20, 30, 40, 50]
5
6 #Convert the list into bytes type array
7 x = bytes(items)
8
9 #Print the array
10 for i in x:
11 print(i)

Sequences
bytes
● Modifying any item in the byte type is not possible
● Example-2:
4 items = [10, 20, 30, 40, 50]
5
7 x = bytes(items)
8
9 #Modifying x[0]
10 x[0] = 11 #Gives an error

bytearray Data-type
Data Types

Sequences
bytearray
● bytearray is similar to bytes
● Difference is items in bytearray is modifiable
● Example-1:
4 items = [10, 20, 30, 40, 50]
5
7 x = bytearray(items)
8
9 x[0] = 55 #Allowed
10
11 #Print the array
12 for i in x:
13 print(i)

Sequences
list
● list is similar to array, but contains items of different data-types
● list can grow dynamically at run-time, but arrays cannot
● Example-1:
3 #Create the list
4 list = [10, -20, 15.5, 'Emertxe', "Python"]
5
6 print(list)
7
8 print(list[0])
9
10 print(list[1:3])
11
12 print(list[-2])
13
14 print(list * 2)

Sequences
tuple
● tuple is similar to list, but items cannot be modified
● tuple is read-only list
● tuple are enclosed within ()
● Example-1:
3 #Create the tuple
4 tpl = (10, -20, 12.34, "Good", 'Elegant')
5
6 #print the list
7 for i in tpl:
8 print(i)

Sequences
range
● range represents sequence of numbers
● Numbers in range are not modifiable
● Example-1:
3 #Create the range of numbers
4 r = range(10)
5
6 #Print the range
7 for i in r:
8 print(i)

Sequences
range
● Example-2:
● Example-3:
10 #Print the range with step size 2
11 r = range(20, 30, 2)
12
13 #Print the range
14 for i in r:
15 print(i)
17 #Create the list with range of numbers
18 lst = list(range(10))
19 print(lst)

Sets
● Set is an unordered collection of elements
● Elements may not appear in the same order as they are entered into the set
● Set does not accept duplicate items
● Types
○ set datatype
○ frozenset datatype

Sets
set
● Example-1:
● Example-2:
● Example-3:
3 #Create the set
4 s = {10, 20, 30, 40, 50}
5 print(s) #Order will not be maintained
8 ch = set("Hello")
9 print(ch) #Duplicates are removed
11 #Convert list into set
12 lst = [1, 2, 3, 3, 4]
13 s = set(lst)
14 print(s)

Sets
set
● Example-5:
● Example-6:
11 #Convert list into set
12 lst = [1, 2, 3, 3, 4]
13 s = set(lst)
14 print(s)
16 #Addition of items into the array
17 s.update([50, 60])
18 print(s)
19
20 #Remove the item 50
21 s.remove(50)
22 print(s)

Sets
frozenset
● Similar to that of set, but cannot modify any item
● Example-1:
● Example-2:
2 s = {1, 2, 3, 4}
3 print(s)
4
5 #Creating the frozen set
6 fs = frozenset(s)
7 print(fs)
9 #One more methos to create the frozen set
10 fs = frozenset("abcdef")
11 print(fs)

Mapping
● Map represents group of items in the form of key: value pair
● dict data-type is an example for map
● Example-1:
● Example-2:
3 #Create the dictionary
4 d = {10: 'Amar', 11: 'Anthony', 12: 'Akbar'}
5 print(d)
6
7 #Print using the key
8 print(d[11])
10 #Print all the keys
11 print(d.keys())
12
13 #Print all the values
14 print(d.values())

Mapping
● Example-3:
● Example-4:
16 #Change the value
17 d[10] = 'Akul'
18 print(d)
19
20 #Delete the item
21 del d[10]
22 print(d)
24 #create the dictionary and populate dynamically
25 d = {}
26 d[10] = "Ram"
27
28 print(d)

Determining the Datatype
Data Types

Determining Datatype of a Variable
● type()
● Example-1:
3 a = 10
4 print(type(a))
5
6 b = 12.34
7 print(type(b))
8
9 l = [1, 2, 3]
10 print(type(l))

Python : Data Types

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