Prerequisites: Python Exception Handling
There are several standard exceptions in Python and NameError is one among them. NameError is raised when the identifier being accessed is not defined in the local or global scope. General causes for NameError being raised are :
1. Misspelled built-in functions:
In the below example code, the print statement is misspelled hence NameError will be raised.
Python3
geek = input()print(geek) |
Output :
NameError: name 'print' is not defined
2. Using undefined variables:
When the below program is executed, NameError will be raised as the variable geek is never defined.
Python3
geeky = input()print(geek) |
Output :
NameError: name 'geek' is not defined
3. Defining variable after usage:
In the following example, even though the variable geek is defined in the program, it is defined after its usage. Since Python interprets the code from top to bottom, this will raise NameError
Python3
print(geek)geek = "Lazyroar" |
Output :
NameError: name 'geek' is not defined
4. Incorrect usage of scope:
In the below example program, the variable geek is defined within the local scope of the assign function. Hence, it cannot be accessed globally. This raises NameError.
Python3
def assign(): geek = "Lazyroar"assign()print(geek) |
Output :
NameError: name 'geek' is not defined
Handling NameError
To specifically handle NameError in Python, you need to mention it in the except statement. In the following example code, if only the NameError is raised in the try block then an error message will be printed on the console.
Python3
def geek_message(): try: geek = "Lazyroar" return neveropen except NameError: return "NameError occurred. Some variable isn't defined."print(geek_message()) |
Output :
NameError occurred. Some variable isn't defined.
