Sum the integers from 1 to 100 in Python

Borislav Hadzhiev

Last updated: Jul 4, 2022

Photo from Unsplash

**To sum the integers from 1 to 100:**

- Pass
`1`

and`100 + 1`

to the`range`

class, e.g.`range(1, 100 + 1)`

. - Pass the
`range`

object to the`sum()`

function. - The
`sum`

function will sum the integers from 1 to 100.

main.py

`num = 100 total = sum(range(1, num + 1)) print(total) # 👉️ 5050 # 👇️ [1, 2, 3, ... 98, 99, 100] print(list(range(1, num + 1))) # ------------------------------------------------ # 👇️ alternatively, you can use a formula total_2 = num * (num + 1) // 2 print(total_2) # 👉️ 5050`

We used the `range()`

class to sum the numbers from 1 to 100.

The range class is
commonly used for looping a specific number of times in `for`

loops and takes
the following arguments:

Name | Description |
---|---|

`start` | An integer representing the start of the range (defaults to `0` ) |

`stop` | Go up to, but not including the provided integer |

`step` | Range will consist of every N numbers from `start` to `stop` (defaults to `1` ) |

Notice that we added

`1`

to the `stop`

value. The `stop`

argument is exclusive, so we had to add `1`

to include `100`

in the result.If you only pass a single argument to the `range()`

constructor, it is
considered to be the value for the `stop`

parameter.

main.py

`num = 100 total = sum(range(num + 1)) print(total) # 👉️ 5050 # 👇️ [1, 2, 3, ... 98, 99, 100] print(list(range(num + 1)))`

The example shows that if the

`start`

argument is omitted, it defaults to `0`

and if the `step`

argument is omitted, it defaults to `1`

.Since the `start`

argument of the range is `0`

, you can omit it and you'd get
the same result.

If values for the

`start`

and `stop`

parameters are provided, the `start`

value is inclusive, whereas the `stop`

value is exclusive.The `sum`

function can be used to calculate the sum of the numbers in the range.

The sum function takes an iterable, sums its items from left to right and returns the total.

main.py

`num = 100 total = sum(range(1, num + 1)) print(total) # 👉️ 5050`

The `sum`

function takes the following 2 arguments:

Name | Description |
---|---|

iterable | the iterable whose items to sum |

start | sums the `start` value and the items of the iterable. `sum` defaults to `0` (optional) |

If you need to get a range with a step, pass a value for the third argument of
the `range()`

class.

main.py

`start = 1 stop = 100 step = 3 total_2 = sum(range(start, stop + 1, step)) print(total_2) # 👉️ 1717 # 👇️ [1, 4, 7, 10, ... 94, 97, 100] print(list(range(start, stop + 1, step)))`

When the `step`

argument is provided, the range will consist of every N numbers
from `start`

to `stop`

.

The value for the `step`

argument defaults to `1`

.

You can also sum the numbers from 1 to 100 using a formula.

main.py

`num = 100 total_2 = num * (num + 1) // 2 print(total_2) # 👉️ 5050`

We multiply 100 by `100 + 1`

and floor-divide the result by `2`

to get the sum
of the integers from 1 to 100.

Division

`/`

of integers yields a float, while floor division `//`

of integers result in an integer.The result of using the floor division operator is that of a mathematical
division with the `floor()`

function applied to the result.