Decision making is the list of conditions occurring during the execution of the program and specifying the actions taken according to the conditions.
It produces TRUE or FALSE as the outcome.
If statement is called as decision making statement.
If Statement
The if statement executes some statements only if some condition holds, or choose statements to execute depending on several mutually exclusive conditions.
There are four type of decision making if statement in python,
1) Simple if
The if statement is used to take a decision based on the condition.
If the condition is satisfied, the statement of true block is executed, otherwise it is moved out.
Syntax
if(condition):
statement
NOTE :
– Must add : after the end of the condition
– Must put 4 space inside the condition, write any statement.
Example :
num = 4
if num > 0:
print(num, " is a positive number.")
OUTPUT
4 is a positive number.
2) if…else Statement
In if…else condition, if the condition is true, it will execute the true block;
Otherwise it will execute the false block.
Syntax
if test expression:
body of if
else:
body of else
Example :
num = 4
if num > 0:
print(num, "is Greater then Zero")
else:
print(num, "is Less then Zero")
OUTPUT
4 is Greater then Zero.
3) if…elif…else Statement
The elif is the short form of else if.
It is used to check for multiple expression.
If the condition is False, it moves to the condition of the next elif block. If whole conditions are False, body of the the else is executed.
Only one block, along with several if…elif…else blocks, are executed according to the state.
The “if” block can contain only one “else” block. But it can hava many “elif” blocks.
Syntax
if test expression:
body of if
elif test expression:
body of elif
else:
body of else
num = -4
if num > 0:
print(num, "is Greater then Zero")
elif num < 0:
print(num, "is Less then Zero")
else:
print(num, "is Zero")
OUTPUT
-4 is Less then Zero.
4) Nested if Statement
In a nested if construct, you can have an if…elif…else construct inside another if…elif…else construct.
Syntax
if test expression:
if test expression:
body of if
else:
body of else
else:
body of else
num = float(input("Enter a number:"))
if num >= 0:
if num == 0:
print("Zero")
else:
print("Greater than Zero")
else:
print("Less than Zero")
OUTPUT
Enter a number:0
Zero
Next we discuss about looping structure in python.
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