Python menyediakan dua fitur yang sangat penting untuk menangani kesalahan tak terduga dalam program Python Anda dan menambahkan kemampuan debugging di dalamnya. Ketika skrip Python menimbulkan Exception, ia harus menangani Exception begitu saja sehingga berhenti dan berhenti. Edit tutorial iniStandard Exceptions
NamaPenjelasan Exception
Kelas dasar untuk semua pengecualian / exception
StopIteration
Dibesarkan ketika metode (iterator) berikutnya dari iterator tidak mengarah ke objek apa pun.
SystemExit
Dibesarkan oleh fungsi sys.exit ().
StandardError
Kelas dasar untuk semua pengecualian built-in kecuali StopIteration dan SystemExit.
ArithmeticError
Kelas dasar untuk semua kesalahan yang terjadi untuk perhitungan numerik.
OverflowError
Dibesarkan saat perhitungan melebihi batas maksimum untuk tipe numerik.
FloatingPointError
Dibesarkan saat perhitungan floating point gagal.
ZeroDivisonError
Dibesarkan saat pembagian atau modulo nol dilakukan untuk semua tipe numerik.
AssertionError
Dibesarkan jika terjadi kegagalan pernyataan Assert.
AttributeError
Dibesarkan jika terjadi kegagalan referensi atribut atau penugasan.
EOFError
Dibesarkan bila tidak ada input dari fungsi raw_input () atau input () dan akhir file tercapai.
ImportError
Dibesarkan saat sebuah pernyataan impor gagal.
KeyboardInterrupt
Dibesarkan saat pengguna menyela eksekusi program, biasanya dengan menekan Ctrl + c.
LookupError
Kelas dasar untuk semua kesalahan pencarian.
IndexError
Dibesarkan saat sebuah indeks tidak ditemukan secara berurutan.
KeyError
Dibesarkan saat kunci yang ditentukan tidak ditemukan dalam kamus.
NameError
Dibesarkan saat pengenal tidak ditemukan di namespace lokal atau global.
UnboundLocalError
Dibesarkan saat mencoba mengakses variabel lokal dalam suatu fungsi atau metode namun tidak ada nilai yang ditugaskan padanya.
EnvironmentError
Kelas dasar untuk semua pengecualian yang terjadi di luar lingkungan Python.
IOError
Dibesarkan saat operasi input / output gagal, seperti pernyataan cetak atau fungsi open () saat mencoba membuka file yang tidak ada.
OSError
Dibangkitkan untuk kesalahan terkait sistem operasi.
SyntaxError
Dibesarkan saat ada kesalahan dengan sintaks Python.
IndentationError
Dibesarkan saat indentasi tidak ditentukan dengan benar.
SystemError
Dibesarkan saat penafsir menemukan masalah internal, namun bila kesalahan ini ditemui juru bahasa Python tidak keluar.
SystemExit
Dibesarkan saat juru bahasa Python berhenti dengan menggunakan fungsi sys.exit (). Jika tidak ditangani dalam kode, menyebabkan penafsir untuk keluar.
TypeError
Dibesarkan saat operasi atau fungsi dicoba yang tidak valid untuk tipe data yang ditentukan.
ValueError
Dibesarkan ketika fungsi bawaan untuk tipe data memiliki jenis argumen yang valid, namun argumen tersebut memiliki nilai yang tidak valid yang ditentukan.
RuntimeError
Dibesarkan saat kesalahan yang dihasilkan tidak termasuk dalam kategori apa pun.
NotImplementedError
Dibesarkan ketika metode abstrak yang perlu diimplementasikan di kelas warisan sebenarnya tidak dilaksanakan.
Python has numerous built-in exceptions that force your program to output an error when something in the program goes wrong.
However, sometimes you may need to create your own custom exceptions that serve your purpose.
Creating Custom Exceptions
In Python, users can define custom exceptions by creating a new class. This exception class has to be derived, either directly or indirectly, from the built-in Exception class. Most of the built-in exceptions are also derived from this class.
Here, we have created a user-defined exception called CustomError which inherits from the Exception class. This new exception, like other exceptions, can be raised using the raise statement with an optional error message.
When we are developing a large Python program, it is a good practice to place all the user-defined exceptions that our program raises in a separate file. Many standard modules do this. They define their exceptions separately as exceptions.py or errors.py (generally but not always).
User-defined exception class can implement everything a normal class can do, but we generally make them simple and concise. Most implementations declare a custom base class and derive others exception classes from this base class. This concept is made clearer in the following example.
Example: User-Defined Exception in Python
In this example, we will illustrate how user-defined exceptions can be used in a program to raise and catch errors.
This program will ask the user to enter a number until they guess a stored number correctly. To help them figure it out, a hint is provided whether their guess is greater than or less than the stored number.
# define Python user-defined exceptions class Error(Exception): """Base class for other exceptions""" pass class ValueTooSmallError(Error): """Raised when the input value is too small""" pass class ValueTooLargeError(Error): """Raised when the input value is too large""" pass # you need to guess this number number = 10 # user guesses a number until he/she gets it right while True: try: i_num = int(input("Enter a number: ")) if i_num < number: raise ValueTooSmallError elif i_num > number: raise ValueTooLargeError break except ValueTooSmallError: print("This value is too small, try again!") print() except ValueTooLargeError: print("This value is too large, try again!") print() print("Congratulations! You guessed it correctly.")Here is a sample run of this program.
Enter a number: 12 This value is too large, try again! Enter a number: 0 This value is too small, try again! Enter a number: 8 This value is too small, try again! Enter a number: 10 Congratulations! You guessed it correctly.We have defined a base class called Error.
The other two exceptions (ValueTooSmallError and ValueTooLargeError) that are actually raised by our program are derived from this class. This is the standard way to define user-defined exceptions in Python programming, but you are not limited to this way only.
Customizing Exception Classes
We can further customize this class to accept other arguments as per our needs.
To learn about customizing the Exception classes, you need to have the basic knowledge of Object-Oriented programming.
Visit Python Object Oriented Programming to start learning about Object-Oriented programming in Python.
Let's look at one example:
class SalaryNotInRangeError(Exception): """Exception raised for errors in the input salary. Attributes: salary -- input salary which caused the error message -- explanation of the error """ def __init__(self, salary, message="Salary is not in (5000, 15000) range"): self.salary = salary self.message = message super().__init__(self.message) salary = int(input("Enter salary amount: ")) if not 5000 < salary < 15000: raise SalaryNotInRangeError(salary)Output
Enter salary amount: 2000 Traceback (most recent call last): File "<string>", line 17, in <module> raise SalaryNotInRangeError(salary) __main__.SalaryNotInRangeError: Salary is not in (5000, 15000) rangeHere, we have overridden the constructor of the Exception class to accept our own custom arguments salary and message. Then, the constructor of the parent Exception class is called manually with the self.message argument using super().
The custom self.salary attribute is defined to be used later.
The inherited __str__ method of the Exception class is then used to display the corresponding message when SalaryNotInRangeError is raised.
We can also customize the __str__ method itself by overriding it.
class SalaryNotInRangeError(Exception): """Exception raised for errors in the input salary. Attributes: salary -- input salary which caused the error message -- explanation of the error """ def __init__(self, salary, message="Salary is not in (5000, 15000) range"): self.salary = salary self.message = message super().__init__(self.message) def __str__(self): return f'{self.salary} -> {self.message}' salary = int(input("Enter salary amount: ")) if not 5000 < salary < 15000: raise SalaryNotInRangeError(salary)Output
Enter salary amount: 2000 Traceback (most recent call last): File "/home/bsoyuj/Desktop/Untitled-1.py", line 20, in <module> raise SalaryNotInRangeError(salary) __main__.SalaryNotInRangeError: 2000 -> Salary is not in (5000, 15000) rangeTo learn more about how you can handle exceptions in Python, visit Python Exception Handling.