In the world of computer programming, encountering errors is a common phenomenon. Take, for example, the KeyError: ‘acc’ in Python. This error often emerges when a specific key that we are trying to access from a dictionary does not exist. Luckily, Python provides eloquent solution to handle such issues and prevent your code from crashing. This includes applying exception handling procedures, employing the get() function, or checking keys before accessing them. With the right approach, this error can be skillfully managed.
Understanding KeyError
KeyError in Python is a type of exception that gets raised when you try to access a dictionary with a key that does not exist. It’s always good coding practice and as per Python’s official documentation, to check if a key is present before attempting to access its value.
#Random example of KeyError
dict1 = {"a":1,"b":2,"c":3}
print(dict1["d"])
In the code above, ‘d’ doesn’t exist in the dictionary dict1, hence it results in KeyError: ‘d’.
Solution to KeyError: ‘acc’
The solution for handling KeyError effectively falls into how you approach accessing items from a dictionary. One way you can avoid this error is by using the get() method when referencing a key.
Here’s how you would do that:
#prints None instead of giving KeyError
print(dict1.get("d"))
The code returns None, as “d” is not in the dictionary. Using get() method, we can also provide a default value that gets returned when the key doesn’t exist.
#prints 'default' instead of None
print(dict1.get("d", 'default'))
Exception Handling is another technique to handle KeyError. This can be done with the help of try-except blocks as shown below.
try:
# code that can raise an exception
print(dict1["d"])
except KeyError:
# Execute this code in case of KeyError
print('Key does not exist')
This code doesn’t terminate the entire program and handles the exception gracefully by printing “Key doesn’t exist”, which is much more user-friendly.
Explaining the code step-by-step
Given the complexity of dealing with KeyErrors, it’s important to break down the code above, bit by bit.
In the first example, we define a dictionary called ‘dict1’ with key-value pairs of {‘a’: 1, ‘b’: 2, ‘c’: 3}. We then try to access a key ‘d’ which does not exist in ‘dict1’. This causes Python to raise a KeyError with ‘d’ as the message.
In the second example, we use the get() method. This Python dictionary method retrieves the value for a given key. If the key is not present, then by default, it returns ‘None’. This prevents Python from raising a KeyError.
In the third example, we set a default value of ‘default’ to get a useful message instead of ‘None’. This is a more informative way to signal that the key was not present.
Lastly, we use a try-except block for exception handling. We write our code under ‘try’ and define what is to be done in case a ‘KeyError’ occurs under ‘except’. This provides a safety net for the code to fall into, instead of breaking or crashing.
Implementing these tactics in your Python programming can greatly help in amp up your coding skills.
