Examples of how to sum a list of numbers in python:

### Using the sum() function

To add all the elements of a list, a solution is to use the built-in function sum(), illustration:

`>>> list = [1,2,3,4]`

`>>> sum(list)`

`10`

Example with float numbers:

`>>> l = [3.1,2.5,6.8]`

`>>> sum(l)`

`12.399999999999999`

Note: it is possible to round the sum (see also Floating Point Arithmetic: Issues and Limitations):

`>>> round(sum(l),1)`

`12.4`

### Iterate through the list:

Example using a for loop:

`>>> list = [1,2,3,4]`

`>>> tot = 0`

`>>> for i in list:`

`... tot = tot + i`

`...`

`>>> tot`

`10`

### Sum a list including different types of elements

Another example with a list containing: integers, floats and strings:

`>>> l = ['a',1,'f',3.2,4]`

`>>> sum([i for i in l if isinstance(i, int) or isinstance(i, float)])`

`8.2`

### Merge a list of "strings":

Note: in the case of a list of strings the function sum() does not work:

`>>> list = ['a','b','c','d']`

`>>> sum(list)`

`Traceback (most recent call last):`

`File "<stdin>", line 1, in <module>`

`TypeError: unsupported operand type(s) for +: 'int' and 'str'`

use the function join() instead:

`>>> ','.join(list)`

`'a,b,c,d'`

`>>> ' '.join(list)`

`'a b c d'`

### References

Links | Site |
---|---|

Built-in Functions | |

Summing elements in a list | stackoverflow |

string — Common string operations | python doc |

Joining elements of a list - Python | stackoverflow |