# Comparisons¶

A Boolean value is a value that can only be True or False. It is called “Boolean” after the mathematician and logician George Boole

Boolean values most often arise from comparison operators. Python includes a variety of operators that compare values. For example, `3` is larger than `1`:

```3 > 1
```
```True
```

`>` is the greater than comparison operator. It takes the value to the left and asks if it is greater than the value to right. The answer can only be `True` or `False`.

The value `True` indicates that the comparison is valid; Python has confirmed this simple fact about the relationship between `3` and `1`.

Python uses the special `bool` type for values that can only be `True` or `False`.

```type(3 > 1)
```
```bool
```

Here we confirm to ourselves that `3` is greater than the result of the expression `1 + 1`:

```3 > 1 + 1
```
```True
```

The value `True` indicates that the comparison is valid; Python has confirmed this simple fact about the relationship between `3` and `1+1`. The full set of common comparison operators are listed below.

Comparison

Operator

True example

False Example

Less than

<

2 < 3

2 < 2

Greater than

>

3>2

3>3

Less than or equal

<=

2 <= 2

3 <= 2

Greater or equal

>=

3 >= 3

2 >= 3

Equal

==

3 == 3

3 == 2

Not equal

!=

3 != 2

2 != 2

Here are some more examples:

```4 < 5
```
```True
```
```4 < 3
```
```False
```
```4 <= 4
```
```True
```

Notice the `==` in the table above.

The double equals `==` is different from the single `=` that we saw before in assignment. Here is assignment.

```a = 4
```

Notice it does not display a value, because it is an assignment, and not an expression.

`==` is different - it’s a comparison operator like `<` or `>`. It checks whether two values are equal, and returns True or False:

```a == 4
```
```True
```

This is an expression, because `==` is an operator, to say how values should be combined, like `+` or `*`.

Strings can also be compared, and their order is alphabetical. A shorter string is less than a longer string that begins with the shorter string.

```"Dog" > "Catastrophe"
```
```True
```
```"Catastrophe" > "Cat"
```
```True
```

Note

This page has content from the Comparison notebook of an older version of the UC Berkeley data science course. See the Berkeley course section of the license file.