Execute a group of lines repeatedly.
Finite looping is the best practice in programming but infinite looping are done because they are easy at times.
Looping variables are generally named i, j, and k, while other names can be used.
General and most common finite looping.
For loop is used to iterate through a sequence or iterator. Lists, tuple, dictionary and string. Syntax:
for value in iterable:
Statements
IN [1]
# Example 1
l = [1, 2, 3, 4, 5]
for i in l:
print(i)
stdout
1
2
3
4
5
IN [2]
# Example 2
s = 'Hello'
for char in s:
print(char)
stdout
H
e
l
l
o
IN [3]
# Error for int
num = 10
for i in num:
print(num)
Error
Traceback (most recent call last):
File "D:\Programming\Python\Jupyter Notebooks\Python_Programming_Notes\temp.py", line 3, in <module>
for i in num:
TypeError: 'int' object is not iterable
Used to create an sequence/object from start to stop in steps
Syntax:
range(stop)
range(start, stop, [step=1])
IN [5]
# Output of range
print(*range(1, 10))
print(*range(10))
stdout
1 2 3 4 5 6 7 8 9
0 1 2 3 4 5 6 7 8 9
IN [6]
#Example 1
for i in range(10):
print(i)
stdout
0
1
2
3
4
5
6
7
8
9
IN [7]
#Example 2
for i in range(0, 20, 2):
print(i)
stdout
0
2
4
6
8
10
12
14
16
18
IN [8]
#Example 3
for i in range(0, 10, 1):
print(i)
stdout
0
1
2
3
4
5
6
7
8
9
Most common for infinite looping. Used to work on numbers or variable length iterables. Preferred for variable conditions
Syntax:
while condition:
Statements
IN [1]
# Example 1:
i = 1
while i<=10:
print(i)
i+=1
stdout
1
2
3
4
5
6
7
8
9
10
IN [1]
# Example 2 using infinite looping
i = 1
while True:
print(i)
if i==100:
break
i+=1
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
Control the execution of the loop
This statement ends the loop when encountered.
Skips the loop execution when encountered.
No change to loop Used when there no statements currently present
IN [2]
i = 1
while i<5:
j=0
while True:
print(i)
j+=1 # j = j+1
if j==4:
break
i+=1
stdout
1
1
1
1
2
2
2
2
3
3
3
3
4
4
4
4
IN [3]
#Example
i = 0
while i<11:
i+=1
if i==5: continue
print(i)
stdout
1
2
3
4
6
7
8
9
10
11
IN [2]
#Example 1
for i in range(10):
if i%2 == 0:
pass
else: print(i)
stdout
1
3
5
7
9
IN [7]
#Example 2
for i in range (10):
if i%2==0: pass
else: print('Odd')
print(i)
stdout
0
Odd
1
2
Odd
3
4
Odd
5
6
Odd
7
8
Odd
9
IN [None]