Python Loops

Python Language Loops

In general, statements are executed sequentially in Computer programming, 

Programming languages provide various control structures that allow for more 
complicated execution paths.

A loop statement allows us to execute a statement or group of statements multiple times.

Python programming language provides two loop structues,

1) while loop
2) for loop to handle loop requirements...
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1) while loop

It repeatedly executes statements while condition is true...

Syntax:

while (condition/expression):
  statement(s);

Example 1 - Print 1 to 10 Numbers.

a=1;
while (a<=10):
    print(a);
    a=a+1;
Output:
1
2
3
4
5
6
7
8
9
10
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Example 2: Read a Number, and calculate sum, and Zero to quit from the loop

a=1;
sum=0;

print ("Enter a Number to add to the sum: ");
print ("Enter 0 to quit.");

while a != 0:
    print ("Current Sum: ", sum);
    a= float(input("Enter Number: "));
    a=float(a);
    sum += a;
print("Total Sum is: ", sum);
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3) Example 3: Print 1 to 5 Numbers in reverse order...

val=5;
while (val >= 1):
  print(val);
  val = val-1;

Output:
5
4
3
2

1
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Python Control Flow Statements
2) for loop

for loop iterates over the items of any sequence, such as a list or a string.

Syntax:

for iterating_var in sequence:
   statement(s);

Example 1:
a= [2, 4, 6, 8, 10, 12, 14];

for num in a:
   print(num);

Output:
2
4
6
8
10
12
14
------------------------
Example 2:
for num in range(5):
  print(num);

output:
0
1
2
3
4
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Note: If you do need to iterate over a sequence of numbers, the built-in function range() comes in handy. It generates arithmetic progressions.
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Note: we can use conditional statements only in our script, or loop statements only, or we can insert loops in Conditional statements and vice versa.
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