What is Lookup Error and reasons for it?

Introduction

In this blog, we have discussed What is Lookup Error and the reasons for it? When a key or index used on a mapping or sequence of a list or dictionary is incorrect or nonexistent, an exception called a “lookup error” is raised. The two different exceptions mentioned are IndexError and KeyError. If you’re getting a “lookup error” in Python, it means that you’re trying to access a variable that doesn’t exist or the error occurs when Python cannot find a value for a given key.

Reasons for Lookup Error

When you get a look-up error in Python, it means that the Python interpreter can’t find the value you’re looking for. This can happen for a few reasons:

1. You may have misspelled the name of the value you’re trying to look up. For example, if you’re trying to look up the value of the “foo” variable, but you accidentally typed “foobar”, you’ll get a look-up error.

2. The value you’re trying to look up may not exist. This can happen if you’re trying to look up a value in a dictionary, but the key you’re using doesn’t exist in the dictionary.

3. The value you’re trying to look up may not be visible. This can happen if you’re trying to look up a global variable in a function, but the function has a local variable with the same name. The local variable will take precedence and the global variable will not be visible.

4. The value you’re trying to look up may be of the wrong type. This can happen if you’re trying to look up a value in a dictionary, but the key you’re using doesn’t point to a dictionary.

5. The name might be defined in a file that’s not on your Python path. If you’re trying to import a module, make sure that the module is in the same directory as your Python file, or is in a directory that’s on your Python path.

Examples

For example, say you have a dictionary called “my_dict” with two key-value pairs. If you try to access a key that doesn’t exist, you’ll get an error:

my_dict = {'key1': 'value1', 'key2': 'value2'}
print(my_dict['key3'])

This will give you a lookup error because ‘key3’ doesn’t exist To avoid this error, you can use the “in” keyword to check if a key exists before trying to access it:

if 'key3' in my_dict:
    print(my_dict['key3']) 
else: 
    print("That key doesn't exist!")

For example, say you have a list of numbers called “numbers”, but you try to access the list using the variable “num”:

numbers = [1, 2, 3]
num = numbers[0]

This will give you a “lookup error” because there is no variable called “num” – only “numbers”. To fix this, you can either create a variable called “num” and set it equal to the list “numbers”:

numbers = [1, 2, 3]
num= numbers

Or you can access the list using the variable “numbers”:

numbers = [1, 2, 3]
num = numbers[0]

Also, read – What is EOF Error, Reasons and Solutions.