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Python If ... Else
Python Conditions and If statements
Python supports common logical conditions from statistics:
- Equals:
a == b - Not Equals:
a != b - Less than:
a < b - Less than or equal to:
a <= b - Greater than:
a > b - Greater than or equal to:
a >= b
These situations can be used in a number of ways, usually "if statements" and loops.
The word "if statement" is written using the keyword if.
Example
If statement:
a = 33
b = 200
if b > a:
print("b is greater than a")
In this example we use two variables, a and b, which are used as part of the statement when checking that b is greater than a. Since a is 33, and b is 200, we know that 200 is greater than 33, so we print to check that "b is greater than a".
Indentation
Python relies on zoom (white area at the beginning of the line) to define the width of the code. Some 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 a pythons method that says "if previous conditions were not true, try this situation".
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 status is true, so we print on screen that "a and b are equal".
Else
Else keyword is holding anything that is not captured by the previous terms.
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 original condition is not true, and the elif status is not true, so we go to else state and print to check that "a is greater than b".
You can also have one else than 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 use, you can put it in the same line as the statement if.
Example
One line if statement:
if a > b: print("a is greater than b")
Short Hand If ... Else
If you have only one statement to use, one is that if, and another, you can put it all in the same line:
Example
One line if else statement:
a = 2
b = 330
print("A") if a > b else print("B")
This process is known as Ternary Operators, or Conditional Expressions.
You can also have many other statements in 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 word and keyword is a logical operator, and is used to compile 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 word or keyword is a logical user, and is used to compile 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 be if statements inside if statements, this is called nested if 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
if the statements can be empty, but if for some reason you have a statement that if we do not have the content, submit a pass statement to avoid finding an error.
Example
a = 33
b = 200
if b > a:
pass