Python NameError: name 'string' is not defined

NameError: name 'string' is not defined

This is a common Python error that occurs when you mistakenly use the word string instead of the correct keyword str for type conversion or related operations in your program.

In this tutorial, we will learn how to recreate this error and understand the solution to handle it effectively.

Recreate NameError

Let us recreate this error to better understand how it occurs.

Python Program

n = 100
s = string(n)

Explanation:

  1. In this program, we attempt to convert a number n into a string using string(n).
  2. However, string is not a built-in function or keyword in Python. The correct keyword for type conversion is str.
  3. This results in a NameError because Python does not recognize string as a defined function.

Output

Traceback (most recent call last):
  File "example1.py", line 2, in <module>
    s = string(n)
NameError: name 'string' is not defined

In the output, Python shows that the name string is not defined, triggering the NameError.

Solution to NameError

To solve this error, you must use the correct built-in Python function. Instead of using string(n), we should use str(n) to convert the number to a string.

Corrected Python Program

n = 100
s = str(n)

Explanation:

  1. In the corrected program, we replace string(n) with str(n), which is the correct Python syntax for converting a number to a string.
  2. The str() function works as intended, and there is no error when it is used.

Additional Examples of NameError

Here are a few more examples where the NameError can occur, with explanations and solutions:

Example 1: Using an Undefined Variable

If you attempt to use a variable that has not been defined, you will get a NameError.

Python Program

print(x)

Output

Traceback (most recent call last):
  File "example2.py", line 1, in <module>
    print(x)
NameError: name 'x' is not defined

Explanation:

  1. In this case, we are trying to print the value of a variable x that hasn't been defined.
  2. To fix this, ensure that x is defined before using it.

Fixed Python Program

x = 10
print(x)

Example 2: Misspelling Built-in Functions

Another common cause of NameError is misspelling a built-in function name.

Python Program

result = maxm(5, 10)

Output

Traceback (most recent call last):
  File "example3.py", line 1, in <module>
    result = maxm(5, 10)
NameError: name 'maxm' is not defined

Explanation:

  1. In this case, the user has misspelled the built-in function max() as maxm().
  2. To solve this, simply correct the function name to max().

Fixed Python Program

result = max(5, 10)

Summary

In this tutorial, we have learned how to handle the NameError in Python, specifically when the name 'string' is used incorrectly instead of the proper str function. We also explored other common causes of NameError, such as:

  • Using undefined variables.
  • Misspelling built-in function names.

Understanding and resolving NameError helps in writing error-free Python programs.

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