Python: check if item or value exists in list or array

Introduction

Sometimes we need to know if an element or value is within a list or array in Python.

There may be a need to simply know if it exists, but it is also possible that we need to obtain the position of an element, that is, its index.

Today we will see how to do it in Python, to check if an element exists in array, as well as to obtain the index of a certain value.

Check if the element exists

We use the operator in, which returns a Boolean indicating the existence of the value within the array. This way:

See the gist on github.

As we can see, it does not matter if our array or list is string or integer type. Of course, they must be primitive data.

Obtain element index

If we want to obtain the index or position, we use the index method of the lists. This way:

See the gist on github.

When we run it, it prints position 1 (remember that the values in the list start at 0). It is important to remember that an error will be generated if the element does not exist in the list. To handle it, we can do something like this:

See the gist on github.

In that case, an exception is generated; because the element does not exist in the list.