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I have seen this data type error come up numerous times while working on my data analytics projects, and recently decided to investigate further. On initial inspection, it can seem a bit of a funny one, but in actual fact, it is quite straight forward.

Lets break it down and see what is going on

So in the below code, there are a number of things:

On line 1 we have a variable that is an integer. If we think about this logically, something that is a single numeric number cannot have a length.

An integer by design is purely to count up a number of apples or no of people, it cannot be viewed as having a length as it is descriptive of the number of occurrences of an object.

data = 100
print(type(data))
print(len(data))

Output Error:
<class 'int'>
Traceback (most recent call last):
  File "object of type int.py", line 3, in <module>
    print(len(data))
TypeError: object of type 'int' has no len()

So for it to in anyway allow a length to be calculated, the object needs to be one of the following data types:

• List
• String
• Tuple
• Dictionary

Opposite to an integer, these are datatypes that have values that would be more appropriate to having values that a length can be calculated on.

data = "100"
print(type(data))
print("Length of string is: ", len(data))

data = [100,200,300]
print(type(data))
print("Length of list is: ", len(data))

data = (100,200,300)
print(type(data))
print("Length of tuple is: ", len(data))

data = {"Age": 1, "Name": 2}
print(type(data))
print("Length of dictionary is: ", len(data))

And the output is:
<class 'str'>
Length of string is:  3
<class 'list'>
Length of list is:  3
<class 'tuple'>
Length of tuple is:  3
<class 'dict'>
Length of dictionary is:  2

In summary, to understand this error and fix it:

An integer describes the number of things that exist for an object, they are actually not the actual object in existence.

Anything that can have a length method applied to it actually exists and can be counted. In the above four examples, they are actually values that you could describe as existing as you can count each one of them.

The explanation here hopefully clears up the matter, if you have any questions leave a comment and I will answer for you!