Hướng dẫn dùng nested ifelse python

If-else conditional statement is used in Python when a situation leads to two conditions and one of them should hold true.

Syntax:

if [condition]:
    code1
else:
    code2

[on_true] if [expression] else [on_false]

Note: For more information, refer to Decision Making in Python [if , if..else, Nested if, if-elif]

Multiple conditions in if statement

Here we’ll study how can we check multiple conditions in a single if statement. This can be done by using ‘and’ or ‘or’ or BOTH in a single statement.

Syntax:

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

• and comparison = for this to work normally both conditions provided with should be true. If the first condition falls false, the compiler doesn’t check the second one. If the first condition is true and the compiler moves to the second and if the second comes out to be false, false is returned to the if statement.
• or Comparison = for this to work normally either condition needs to be true. The compiler checks the first condition first and if that turns out to be true, the compiler runs the assigned code and the second condition is not evaluated. If the first condition turns out to be false, the compiler checks the second, if that is true the assigned code runs but if that fails too, false is returned to the if statement.

The following examples will help understand this better:
PROGRAM 1: program that grants access only to kids aged between 8-12

age=

[on_true] if [expression] else [on_false]

0

[on_true] if [expression] else [on_false]

1

[on_true] if [expression] else [on_false]

2=

[on_true] if [expression] else [on_false]

4

[on_true] if [expression] else [on_false]

5

[on_true] if [expression] else [on_false]

6

[on_true] if [expression] else [on_false]

7=

[on_true] if [expression] else [on_false]

9

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

0

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

1

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

2

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

3

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

4

[on_true] if [expression] else [on_false]

5

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

6

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

7

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

1

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

2

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

3

SORRY ! YOU ARE NOT ALLOWED. BYE !

1

[on_true] if [expression] else [on_false]

5

Output:

SORRY ! YOU ARE NOT ALLOWED. BYE !

PROGRAM 2:

program that checks the agreement of the user to the terms

SORRY ! YOU ARE NOT ALLOWED. BYE !

3=

SORRY ! YOU ARE NOT ALLOWED. BYE !

5

[on_true] if [expression] else [on_false]

1

SORRY ! YOU ARE NOT ALLOWED. BYE !

7==

PROGRAM 2:

0

PROGRAM 2:

1

SORRY ! YOU ARE NOT ALLOWED. BYE !

3==

PROGRAM 2:

5

PROGRAM 2:

6

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

1

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

2

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

3

YOU SAID NO

0

[on_true] if [expression] else [on_false]

5

YOU SAID NO

2

SORRY ! YOU ARE NOT ALLOWED. BYE !

7==

SORRY ! YOU ARE NOT ALLOWED. BYE !

5

PROGRAM 2:

1

SORRY ! YOU ARE NOT ALLOWED. BYE !

3==

9  is the largest

1

PROGRAM 2:

6

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

1

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

2

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

3

9  is the largest

6

[on_true] if [expression] else [on_false]

5

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

6

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

7

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

1

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

2

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

3

working

3

[on_true] if [expression] else [on_false]

5

Output:

YOU SAID NO

PROGRAM 3: program to compare the entered three numbers

working

5=

working

7

working

8= age0

age1= age3

[on_true] if [expression] else [on_false]

1age5

[on_true] if [expression] else [on_false]

6 age7

[on_true] if [expression] else [on_false]

6 age9=

working

8

[on_true] if [expression] else [on_false]

6 =3= =5

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

1

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

2=8=9

[on_true] if [expression] else [on_false]

5

YOU SAID NO

2

[on_true] if [expression] else [on_false]

02

[on_true] if [expression] else [on_false]

6

[on_true] if [expression] else [on_false]

04

[on_true] if [expression] else [on_false]

6

[on_true] if [expression] else [on_false]

06=

working

5

[on_true] if [expression] else [on_false]

6

[on_true] if [expression] else [on_false]

10= =5

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

1

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

2

[on_true] if [expression] else [on_false]

15=9

[on_true] if [expression] else [on_false]

5

YOU SAID NO

2

[on_true] if [expression] else [on_false]

19

[on_true] if [expression] else [on_false]

6

[on_true] if [expression] else [on_false]

21

[on_true] if [expression] else [on_false]

6

[on_true] if [expression] else [on_false]

23=

working

5

[on_true] if [expression] else [on_false]

6

[on_true] if [expression] else [on_false]

27=

[on_true] if [expression] else [on_false]

29

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

1

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

2

[on_true] if [expression] else [on_false]

32=9

[on_true] if [expression] else [on_false]

5

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

6

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

7

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

1

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

2

if [cond1 AND/OR COND2] AND/OR [cond3 AND/OR cond4]:
    code1
else:
    code2

3

[on_true] if [expression] else [on_false]

40

[on_true] if [expression] else [on_false]

5

Output:

9  is the largest

Not just two conditions we can check more than that by using ‘and’ and ‘or’.
PROGRAM 4:

working

5=

[on_true] if [expression] else [on_false]

44

working

8=

[on_true] if [expression] else [on_false]

44

age1=

[on_true] if [expression] else [on_false]

44

[on_true] if [expression] else [on_false]

1

[on_true] if [expression] else [on_false]

52==

[on_true] if [expression] else [on_false]

44

[on_true] if [expression] else [on_false]

6

working

8==

[on_true] if [expression] else [on_false]

44

[on_true] if [expression] else [on_false]

6 age1==

[on_true] if [expression] else [on_false]

44

PROGRAM 2:

6