In this example we use two variables, a and b, which are used as part of the if statement to test whether b is greater than a. As a is 33, and b is 200, we know that 200 is greater than 33, and so we print to screen that "b is greater than a".
Indentation
Python relies on indentation [whitespace at the beginning of a line] to define scope in the code. Other programming languages often use curly-brackets for this purpose.
Example
If statement, without indentation [will raise an error]:
a = 33
b = 200
if b > a:
print["b is greater than a"] # you will get an error
Elif
The elif keyword is pythons way of saying "if the previous conditions were not true, then try this condition".
Example
a = 33
b = 33
if b > a:
print["b is greater than a"]
elif a == b:
print["a and b are equal"]
In this example a is equal to b, so the first condition is not true, but the elif condition is true, so we print to screen that "a and b are equal".
Else
The else keyword catches anything which isn't caught by the preceding conditions.
Example
a = 200
b = 33
if b > a:
print["b is greater than a"]
elif a == b:
print["a and b are equal"]
else:
print["a is greater than b"]
In this example a is greater than b, so the first condition is not true, also the elif condition is not true, so we go to the else condition and print to screen that "a is greater than b".
You can also have an else
without the elif
:
Example
a = 200
b = 33
if b > a:
print["b is greater than a"]
else:
print["b is not greater than a"]
Short Hand If
If you have only one statement to execute, you can put it on the same line as the if statement.
Short Hand If ... Else
If you have only one statement to execute, one for if, and one for else, you can put it all on the same line:
Example
One line if else statement:
a = 2
b = 330
print["A"] if a > b else print["B"]
This technique is known as Ternary Operators, or Conditional Expressions.
You can also have multiple else statements on the same line:
Example
One line if else statement, with 3 conditions:
a = 330
b = 330
print["A"] if a > b else print["="] if a == b else print["B"]
And
The and keyword is a logical operator, and is used to combine conditional statements:
Example
Test if a
is greater than b
, AND if c
is greater than a
:
a = 200
b = 33
c = 500
if a > b and c > a:
print["Both conditions are True"]
Or
The or
keyword is a logical operator, and is used to combine conditional statements:
Example
Test if a
is greater than b
, OR if a
is greater than c
:
a = 200
b = 33
c = 500
if a > b or a > c:
print["At least one of the conditions is True"]
Nested If
You can have else
2 statements inside else
2 statements, this is called nested else
2 statements.
Example
x = 41
if x > 10:
print["Above ten,"]
if x > 20:
print["and also above 20!"]
else:
print["but not above 20."]
The pass Statement
else
2 statements cannot be empty, but if you for some reason have an else
2 statement with no content, put in the else
7 statement to avoid getting an error.
Use the if
statement to specify a block of Java code to be executed if a condition is
if [20 > 18] {
System.out.println["20 is greater than 18"];
}
3.Syntax
if [condition] {
// block of code to be executed if the condition is true
}
Note that if
is in lowercase letters. Uppercase letters [If or IF] will generate an error.
In the example below, we test two values to find out if 20 is greater than 18. If the condition is
if [20 > 18] {
System.out.println["20 is greater than 18"];
}
3, print some text:Example
if [20 > 18] {
System.out.println["20 is greater than 18"];
}
Try it Yourself »
We can also test variables:
Example
int x = 20;
int y = 18;
if [x > y] {
System.out.println["x is greater than y"];
}
Try it Yourself »
Example explained
In the example above we use two variables, x and y, to test whether x is greater than y [using the
if [20 > 18] {
System.out.println["20 is greater than 18"];
}
6 operator]. As x is 20, and y is 18, and we know that 20 is greater than 18, we print to the screen that "x is greater than y".The else Statement
Use the else
statement to specify a block of code to be executed if the condition is
if [20 > 18] {
System.out.println["20 is greater than 18"];
}
8.Syntax
if [condition] {
// block of code to be executed if the condition is true
} else {
// block of code to be executed if the condition is false
}
Example
int time = 20;
if [time < 18] {
System.out.println["Good day."];
} else {
System.out.println["Good evening."];
}
// Outputs "Good evening."
Try it Yourself »
Example explained
In the example above, time [20] is greater than 18, so the condition is
if [20 > 18] {
System.out.println["20 is greater than 18"];
}
8. Because of this, we move on to the else
condition and print to the screen "Good evening". If the time was less than 18, the program would print "Good day".The else if Statement
Use the
if [20 > 18] {
System.out.println["20 is greater than 18"];
}
0 statement to specify a new condition if the first condition is if [20 > 18] {
System.out.println["20 is greater than 18"];
}
8.Syntax
if [condition1] {
// block of code to be executed if condition1 is true
} else if [condition2] {
// block of code to be executed if the condition1 is false and condition2 is true
} else {
// block of code to be executed if the condition1 is false and condition2 is false
}
Example
int time = 22;
if [time < 10] {
System.out.println["Good morning."];
} else if [time < 18] {
System.out.println["Good day."];
} else {
System.out.println["Good evening."];
}
// Outputs "Good evening."
Try it Yourself »
Example explained
In the example above, time [22] is greater than 10, so the first condition is
if [20 > 18] {
System.out.println["20 is greater than 18"];
}
8. The next condition, in the if [20 > 18] {
System.out.println["20 is greater than 18"];
}
0 statement, is also if [20 > 18] {
System.out.println["20 is greater than 18"];
}
8, so we move on to the else
condition since condition1 and condition2 is both if [20 > 18] {
System.out.println["20 is greater than 18"];
}
8 - and print to the screen "Good evening".