## if, else, and elif Statements

Read this for more on conditional statements.

### 6. Boolean operators and expressions

#### Booleans and Boolean operators

A Boolean refers to a value that is either **True **or **False**. These two are constants in Python.

- we can assign a Boolean value by specifying True or False,

x = True

- an expression can evaluate to a Boolean value

y > 10

#### and operator

The Boolean expression a and b is True if and only if both a and b are True.

a | b | a and b |
---|---|---|

True | True | True |

True | False | False |

False | True | False |

False | False | False |

**Examples**: assume that a = 8 and b = 3, then the Boolean value of

1) ( a > 10 ) and ( b < 5 ) is False

2) ( a != 10 ) and ( b > 1 ) is True

#### or operator

The Boolean expression a or b is False if and only if both a and b are False.

a | b | a or b |
---|---|---|

True | True | True |

True | False | True |

False | True | True |

False | False | False |

**Examples**: assume that a = 8 and b = 3, then the Boolean value of

1) ( a > 10 ) or ( b < 5 ) is True

2) ( a == 10 ) or ( b > 1 ) is True

#### not operator

The Boolean expression not a is False when a is True, and is True when a is False.

a | not a |
---|---|

True | False |

False | False |

**Examples**: assume that a = 8 and b = 3, then the Boolean value of

1) not ( a > 10 ) is True

2) not ( a * 10 > 20 ) is False

#### Booleans and Boolean operators

Consider the following code fragment:if letter == 'a' or letter == 'b': print("Help!") elif letter == 'c' or letter == 'd': print("We are in trouble!") else: print("We are good!")

If letter = "a", then we will get: **Help!**

if letter == 'a' or letter == 'b': print("Help!") elif letter == 'c' or letter == 'd': print("We are in trouble!") else: print("We are good!")

If letter = "c", then we will get:** We are in trouble!**