Python is one of the most popular programming languages in the world. It is easy to learn, quite powerful, and by far the most popular language for developing artificial intelligence.
So, it is no wonder that budding programmers like to pick it up. However, as with any programming language, there are learning and growing pains. Users run into programming errors all the time, and if they are not experienced, they can become scared and see the errors as roadblocks.
The reality is far from it. Python error messages are designed to help you figure out problems in your code and fix them. Treat them like guidance tools, and your programming skills will improve.
Today, we are going to teach you how to understand some of the most common Python error messages. After reading this article, they should not appear to be daunting anymore.
1. SyntaxError
A syntax error occurs when you write code that doesn’t follow the rules of Python. As such, it cannot be parsed, and your program grinds to a halt. Common causes of syntax errors are:
- Spelling mistakes
- Incorrect symbols
- Incorrect placement of punctuation, keywords, operators, and delimiters.
The good thing is that your code compiler will tell you exactly where the error occurred, so you can fix it quickly. Here’s an example you can check to understand this error.
| if x == 10
print(“x is 10”) # Missing colon after the if statement |
This is a simple line of code that says compare X to see if it equals 10. Then print ‘X is 10’ if the comparison is true. However, the problem with this code is that the ‘semi-colon’ used to end lines of code is missing from the “IF” statement.
Since Python clearly points to the problematic line, you can see that you missed a semicolon and fix the error.
2. NameError
A name error occurs when you try to use a variable or function that you have not defined in the program. As you know, you have to define all variables beforehand. If you don’t, then you will get name errors or other weird behavior.
Take a look at this sample code. In this line, let’s assume the variable “total_amount” has not been declared. So, when you use the print statement, Python will throw a NameError.
| print(total_amount) # total_amount is not defined |
The good thing is that the error typically tells you the exact name causing the problem, making it easy to locate and correct.
3. TypeError
A Type Error is a typical rookie mistake. It occurs when the programmer tries to use an operation (such as addition or subtraction) on a data type that is not compatible with it.
For example, strings and integers can’t be “added” to each other. Either both have to be strings or both have to be integers. Take a look at this example.
| age = 25
message = “I am ” + age # Cannot concatenate string and integer |
In this code, age is an integer, while ‘I am’ is a string. They cannot be concatenated due to the differing data types. If you do want to do that, then you have to use a special function called ‘str.’ This function changes the data type of a variable. So you can write ‘str (age) before “message =…” and the code will work.
If you receive this type of error, then don’t feel bad about it; it means you tried to experiment and that your understanding of Python is improving.
4. ValueError
A value error occurs when you try to assign the wrong type of value to a variable. For example, if you define an integer variable, but then you try to assign a string to it, you will get a value error.
Here’s an example:
| number = int(“hello”) # Cannot convert non-numeric string to integer |
Just make sure you are assigning the correct type of value to the variable, and you will be fine.
5. ImportError / ModuleNotFoundError
Import errors occur when you try to use a library or module that you didn’t install on your system. For example, if you want to use numpy to do mathematical operations, you need to ensure that you have installed it using PIP. Then you also need to initialize it in your code.
If the installation has failed or is incorrect, you will get the import error. It is also possible to get an import error due to incorrect spelling. So, make sure you are using the correct spelling.
6. ConnectionError / HTTPError (API-related)
If you are using Python to write scripts or use APIs, then you might have run into a connection error or an HTTP error.
This often occurs during external API communication and can happen due to several reasons.
- Incorrect spelling of the API domain
- The domain is down or otherwise inaccessible
The solution for the first one is to check your spelling, and the solution for the second reason is to do a DNS lookup for the API domain to see if it’s working or not.
If the domain is down and you have confirmed it with a DNS lookup, then all you can do is lodge a ticket and wait. However, if you are a beginner, it is unlikely you will run into this error very often.
7. AttributeError
An attribute error occurs when you mistakenly try to access a method or an attribute for an object, but the attribute/method doesn’t exist.
There are plenty of data types in Python, and they all work with specific methods and attributes. You cannot switch their attributes or methods between them.
Take a look at the following example. There is a string variable in the code, and it is being mistakenly used with the append method, which is a list method, not a string method.
| name = “Alice”
name.append(“B”) # Strings do not have an ‘append’ method |
So, the code will throw an attribute error and fail to parse. This is basically a knowledge issue and can be curbed by improving your understanding of object types and which methods work with each type.
8. KeyError
When dealing with data structures, specifically a dictionary, you can get a key error if you try to access a non-existent key.
In the example below, we have a dictionary called person with only one key-value pair, which is “Name: Alice”. There are no other keys or values.
If you were to try to access the Person dictionary and try to call a key like “age”, you would get the key error.
| person = {“name”: “Alice”}
print(person[“age”]) # ‘age’ key doesn’t exist |
To prevent this error, you can either create a key-value pair so that it exists or you can use the person.get(“age”) command instead. The get command doesn’t throw the error; instead, it simply returns “None’ if the key isn’t found.
Final Thoughts
Python error messages are not meant to frustrate developers; they are meant to help them. They’re powerful diagnostic tools that point out what went wrong in your code and where.
As you practice and encounter more errors, you will find that your attention to detail improves and you start writing cleaner and robust code. So, don’t be afraid of the errors, start Googling, and get error-correcting.
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