# Data Types

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&#x20;[Basics](http://python.swaroopch.com/basics.html)

## Data Types

A data type is simply the type of data we can store in programs. Python has a fairly small set of data types.

* integer (int) which are numbers like `1`, `4`, `7`
* floating point (float) which are numbers like `3.5`, `6.2`, `8.9`
* string (str) which is simply a collection of characters (any character you

  &#x20; wish like: `askj#@lk14p`) surrounded by quotes (' or ")
* boolean (bool) which can be either `True` or `False` (see \[George

  &#x20;  Boole]\(<https://en.wikipedia.org/wiki/George_Boole>)). `True` and `False` are

  &#x20;  special words in Python and are reserved for their raw values. That means

  &#x20;  that you may not use them when naming things.

## Operators

You can manipulate data using operators (+, -, \*, /, <, >, etc). The obvious math operations like `1+2` work but we also have other operations like `'I like ' + 'britney'`. This operation will concatenate (or combine) the two strings into a single string.

Try printing out to the terminal screen some math operations:

```python
# use the exponentiation operator
print(2**3)
print('reed likes' + ' to program')
```

Running this program should produce: `8` and `reed likes to program`.

In addition to the math operators and a few that work on strings there are also a number of booleans operators (<, >, <=,

> \=, ==, !=, not, or, and).

```python
print(3 < 4)
print('4' != 4)  # strings are never equal to numbers
print(42 == 42)
print(1 < 2 and 2 < 3)
```

Running this program should produce: `True` 4 times.

&#x20;*Try printing out some expressions using various operators!*

## Variables

Variables are simply a way to keep track of the values you want to manipulate. They act as boxes to hold data types. You can create a variable by doing the following:

```python
my_name = 'reed'
my_height = 70.9375
happy = True
```

The first variable will hold a string with the value of `reed`, the second will hold an floating point with the value of `70.9375`, and the third will hold a boolean with the value of `True`.

Variable names have specific rules. They have to be a single word (no spaces) and can have numbers, letters or underscores. They cannot begin with a number and are case sensitive (meaning `SPAM` does not equal `spam`).

&#x20;*Try storing the results of your previous operations in variables. Then print them out!*

## Tip

You can combine strings (concatenate) using the `+` operator but this gets pretty inefficient if you do it in loops (which we will learn about in a later lesson). It is always a good idea to combine strings using string formatting. You can create a string that has special tokens inside of it and then replace those tokens with the values you supply.

```python
name = 'reed'
height = 72
eye_color = 'blue'
print("Hello! My name is %s. I am %d inches tall and have %s eyes".format(name, height, eye_color))
```

Doing this will be more efficient and ends up being more readable in my opinion. One thing to keep in mind though is that if you have a decimal number (like `height` in the example), you need to use a `%d` instead of a `%s`. For a list of format characters and what they mean check out the [Python documentation](https://docs.python.org/2.4/lib/typesseq-strings.html). [Dive Into Python](http://www.diveintopython.net/native_data_types/formatting_strings.html) also has a really great article that goes into greater detail.


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