Generators in Python:

Syntax similar to function but are used to generate values.

New instances are not created everytime the function is called.

Types:

1. Function type generators
2. Inline generators

1. Function type:

Definition as a function. Difference is that it uses yield instead of return.

IN [1]

def my_first_generator(): # Defining a generator
    i = 1
    while i<=100:
        yield i
        i += 1
for j in my_first_generator(): # Calling a generator
    print(j, end=' ')

stdout

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 

2. Inline generators:

List comprehension inside paranthesis give inline generators.
Syntax: generator_name = (...List Comprehension...)

IN [1]

gen = ( 2*i for i in range(10) ) # Definition of a generator
for i in gen:
    print(i)

stdout

0
2
4
6
8
10
12
14
16
18

next method:

Returns the next element of the generator.

Syntax: generator.__next__()

IN [5]

def my_first_generator(): # Defining a generator
    i = 1
    while i<=100:
        yield i
        i += 1
gen = my_first_generator()
for j in range(50): # Calling a generator
    print(gen.__next__())

stdout

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50

IN [7]

gen = ( 2*i for i in range(10) ) # Definition of a generator
for i in range(5):
    print(gen.__next__())

stdout

0
2
4
6
8