# Python sum() method

sum is a very useful function in python, but be careful how you use it, the first time I used it, I used it like this.

```
s = sum(1,2,3)
```

It's a tragedy. You would see this error:

```
>>>sum = sum(1,2)
TypeError: 'int' object is not iterable
```

Actually, sum() is a list, example:

```
sum([1,2,3])
sum(range(1,11))
```

There's one more interesting use.

```
a = range(1,11)
b = range(1,10)
c = sum([item for item in a if item in b])
print(c)
```

**Related course:** Complete Python Programming Course & Exercises

## python sum() example

The example below shows some more uses of the sum function:

```
>>>sum = sum([1,2,3]) # in list
6
>>> sum = sum([1,2,3],5) #in list +start
9
>>> sum = sum((1,2,3)) #in tuple
6
>>> sum = sum({1,2,3}) #in set
6
>>> sum = sum({1:5,2:6,3:7}) #in dictionary key
6
>>> sum = sum(range(1,4)) #in range()
```

## numpy sum

You can also use the sum() function in numpy.

```
>>> import numpy as np
>>> a=np.sum([[0,1,2],[2,1,3]])
>>> a
9
>>> a.shape
()
>>> a=np.sum([[0,1,2],[2,1,3]],axis=0)
>>> a
array([2, 2, 5])
>>> a.shape
(3,)
>>> a=np.sum([[0,1,2],[2,1,3]],axis=1)
>>> a
array([3, 6])
>>> a.shape
(2,)
```