Python try import error

Python try catch exceptions with simple examples

A program in python terminates as it encounters an error. Mainly there are two common errors; syntax error and exceptions.

Python exceptions are errors that happen during execution of the program. Python try and except statements are one of the important statements that can catch exceptions. I

n this tutorial we will cover Python exceptions in more details and will see how python try except statements help us to try catch these exceptions along with examples. Moreover, we will also learn about some of the built-in exceptions in python and how to use them.

Difference between Python Exception and Error

Python exceptions and errors are two different things. There are some common differences between them which distinguish both from each other. These are the following differences between them.

• Errors cannot be handled, while Python exceptions can be catchd at the run time.
• The error indicates a problem that mainly occurs due to the lack of system resources while Exceptions are the problems which can occur at runtime and compile time. It mainly occurs in the code written by the developers.
• An error can be a syntax (parsing) error, while there can be many types of exceptions that could occur during the execution.
• An error might indicate critical problems that a reasonable application should not try to catch, while an exception might indicate conditions that an application should try to catch.

Different type of errors in Python

Errors are the problems in a program due to which the program will stop the execution. There can be different types of errors which might occur while coding. Some of which are Syntax error, recursion error and logical error. In this section we will closely look at each of these errors in more detail.

Syntax error in Python

When we run our python code, the first thing that interpreter will do is convert the code into python bytecode which then will be executed. If the interpreter finds any error/ invalid syntax during this state, it will not be able to convert our code into python code which means we have used invalid syntax somewhere in our code. The good thing is that most of the interpreters show us/give hints about the error which helps us to resolve it. If you are a beginner to Python language, you will see syntaxError a lot while running your code.

Here is an example showing the syntax error.

# defining variables a = 10 b = 20

Output:

You can see the python is indicating the error and pointing to the error.

Recursion error in Python

This recursion error occurs when we call a function. As the name suggests, recursion error when too many methods, one inside another is executed with one an infinite recursion.

See the following simple example of recursion error:

# defining a function: def main(): return main() # calling the function main()

Output:

See the last line, which shows the error. We get a recursionError because the function calls itself infinitely times without any break or other return statement.

Python exceptions

Sometimes, even if the syntax of the expression is correct, it may still cause an error when it executes. Such errors are called logical errors or exceptions. Logical errors are the errors that are detected during execution time and are not unconditionally fatal. Later in the tutorial we will cover how to catch these errors using python try except method.

Again there can be many different kinds of Python exceptions you may face. Some of them are typeError , ZeroDivisionError , importError and many more. We will see some of the examples of exceptions here.

See the example which gives typeError when we try to add two different data types.

# string data type name = "bashir" # integer data type age = 21 # printing by adding int and string print(age + name)

Here is one more example which gives zeroDivisionError when we try to divide some number by zero.

 print(23/0) ZeroDivisionError: division by zero

Now see the last example of import module error . This error occurs when we import a module that does not exist.

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mypy bug with try/except conditional imports #1153

mypy bug with try/except conditional imports #1153

Comments

try: import simplejson except ImportError: import json as simplejson 

resulst in the error error: Name ‘simplejson’ already defined

The text was updated successfully, but these errors were encountered:

Note that #649 was closed; a buch of «leftover» bugs were opened in its
place, but I don’t see one that matches this pattern, so I think it’s a new
case.

On Mon, Jan 25, 2016 at 3:19 PM, Ryan Gonzalez notifications@github.com
wrote:

Related to #649 #649.

—
Reply to this email directly or view it on GitHub
#1153 (comment).

—Guido van Rossum (python.org/~guido)

Another example from #2251 (reported by @RitwikGupta):

try: # Python 3 from urllib.request import urlopen except ImportError: # Python 2 from urllib2 import urlopen

This python code generates an error. It’s a common idiom and it would be good if mypy could check for it in some way.

try: import cPickle as pickle except ImportError: import pickle

$ mypy --py2 --silent-imports bad.py bad.py:4: error: Name 'pickle' already defined 

The current workaround is to add a # type: ignore comment. For example:

try: import cPickle as pickle except ImportError: import pickle # type: ignore # 

FYI, this doesn’t appear to work with sub-modules:

# This will error try: import foo.bar except ImportError: foo = None # type:ignore

This seems to work though:

# This will pass try: import doesnt.exist # type:ignore except ImportError: doesnt = None # So will this try: import collections.abc # type:ignore except ImportError: collections = None assert doesnt is None assert collections is not None

This is particularly difficult when the import that’s happening is a typing import.

$ mypy --version mypy 0.530 $ cat no_try.py from typing import Dict, Any JSON = Dict[str, Any] def accept(obj: JSON) -> Any: return obj.pop('hello') $ mypy --ignore-missing-imports no_try.py

$ cat with_try.py try: from typing import Dict, Any except: from backports.typing import Dict, Any # type: ignore JSON = Dict[str, Any] def accept(obj: JSON) -> Any: return obj.pop('hello') $ mypy --ignore-missing-imports with_try.py with_try.py:10: error: Invalid type "with_try.JSON" with_try.py:11: error: JSON? has no attribute "pop" 

This program should typecheck.

@quodlibetor I don’t think your particular case is a bug. mypy has special treatment of typing module, so your imports should be written as:

from typing import TYPE_CHECKING if TYPE_CHECKING: from typing import Dict, Any else: try: from typing import Dict, Any except ImportError: from backports.typing import Dict, Any

If your version of typing doesn’t have TYPE_CHECKING , then use:

MYPY = False if MYPY: # special imports from typing else: # actual runtime implementation

mypy will understand this.

Hmm, okay, I’ve verified that that works.

$ cat with_try.py MYPY = False if MYPY: from typing import Dict, Any else: try: from typing import Dict, Any except: from backports.typing import Dict, Any JSON = Dict[str, Any] def accept(obj: JSON) -> Any: return obj.pop('hello') $ mypy with_try.py 

I think that I would still be inclined to describe the current behavior as a bug that has a workaround. Would you agree that it is at least as a UX problem?

The if MYPY trick brings the total number of lines of boilerplate to type check a module up to 8, for what would be a single-line import if you were only supporting the most modern python. Even just supporting python 3.5 if you want new items from the typing module means that we jump from 1 to 8 lines of code. It’s not even «simple» code. It’s also not the obvious first way that I would write that code. obviously.

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Python ImportError

In Python, we use “import” when we want to import any specific module in the Python program. In Python, to make or to allow the module contents available to the program we use import statements. Therefore when importing any module and there is any trouble in importing modules to the program then there is a chance of ImportError occurrence. In this article, we will discuss such error which generally occurs if there is an invalid declaration of import statement for module importing and such problems also known as ModuleNotFoundError in the latest versions of Python such as 3.6 and newer versions.

Examples of ImporError in Python

In Python, when we want to include the module contents in the program then we have to import these specific modules in the program. So to do this we use “import” keyword such as import statement with the module name. When writing this statement and the specified module is not written properly or the imported module is not found in the Python library then the Python interpreter throws an error known as ImportError.

There are two conditions when the ImportError will be raised. They are

Now let us demonstrate in the below program that throws an ImportError.

Example #1

Now suppose we are trying to import module “request” which is not present or saved in Python drive where we need to download it. Let us see a small example below:

In the above sample code, we can see that we are importing a module named “request” which is not present in the downloaded Python library. Therefore it throws an ImportError which gives the message saying no module named “request”. As each module when downloaded or inbuilt it has its own private symbol table where all defined module is saved by creating separate namespace. Therefore if the module is present then there is no occurrence of such error.

In Python, there is another way of importing modules in the program and if this statement also fails then also ImportError occurs. Let us see the example below:

Example #2

In the above program, we can see another way of importing modules. This also throws ImportError if the module is not present in the private Python library.

The above two methods of importing modules in the program throw an error if the module is not present. Therefore catch such errors in exception handling concept it provides an ImportError exception which has the Python exception hierarchy as BaseException, Exception, and then comes ImportError. In Python, even moduleNotFoundError is also the same as an ImportError exception. Now let us below how to handle such error in the Python program using try and except blocks of exception handling.

Example #3

print("Program to demonstrate to handle ImportError:") print("\n") try: from crypt import pwd except ImportError as ie: print("It cannot import module and submodule", ie)

In the above program, we can see when we are trying to import the “crypt” module and we are handling this ImportError using try and except the block of exception handling. This is one way to avoid the error message to be printed.

To avoid such an ImportError exception we saw above the use of exception handling. But still, it will display the error message on the output screen. Such error occurs when there is no module present in the Python private table. To avoid this we can directly download this module from the Internet to the Python IDE. Let us see how we can avoid this ImportError we need to download the module and we will not get this error and this done as below:

If pip is installed we can directly run this to install the module. Else first we need to install the pip and then install the other packages.

Another way to download the module is to download the package directly through the Internet by downloading the module and unzip the folder and save that folder where the Python software is saved.

Conclusion – Python ImportError

In this article, we conclude that the ImportError is an exception in Python hierarchy under BaseException, Exception, and then comes this Exception. In Python, ImportError occurs when the Python program tries to import module which does not exist in the private table. This exception can be avoided using exception handling using try and except blocks. We also saw examples of how the ImportError occurs and how it is handled.

Recommended Articles

This is a guide to Python ImportError. Here we also discuss the introduction and working of import error in python along with its different examples and its code implementation. You may also have a look at the following articles to learn more –

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