Python 3 Os Error
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you have probably seen some. There are (at least) two distinguishable kinds of errors: syntax errors and exceptions. 8.1. Syntax Errors¶ Syntax
Valueerror Python
errors, also known as parsing errors, are perhaps the most common kind python custom exception of complaint you get while you are still learning Python: >>> while True print('Hello world') File "
Python Raise Valueerror
the error was detected. The error is caused by (or at least detected at) the token preceding the arrow: in the example, the error is detected at the function print(), since a colon (':') is missing before it. File name and line number are printed so you know where to look in case the input came from a
Python Filenotfounderror
script. 8.2. Exceptions¶ Even if a statement or expression is syntactically correct, it may cause an error when an attempt is made to execute it. Errors detected during execution are called exceptions and are not unconditionally fatal: you will soon learn how to handle them in Python programs. Most exceptions are not handled by programs, however, and result in error messages as shown here: >>> 10 * (1/0) Traceback (most recent call last): File "
code: Lib/os.py This module provides a portable way of using operating system dependent functionality. If you just want to read or write a file see altsep6, python programming can handle every error implicitly a) true b) false if you want to manipulate paths, see the altsep5 module, and
Python Exception Class Methods
if you want to read all the lines in all the files on the command line see python attributeerror object has no attribute the altsep4 module. For creating temporary files and directories see the altsep3 module, and for high-level file and directory handling see the altsep2 module. Notes on the availability of https://docs.python.org/3/tutorial/errors.html these functions: The design of all built-in operating system dependent modules of Python is such that as long as the same functionality is available, it uses the same interface; for example, the function altsep1 returns stat information about path in the same format (which happens to have originated with the POSIX interface). Extensions peculiar to a particular operating https://docs.python.org/3/library/os.html system are also available through the altsep0 module, but using them is of course a threat to portability. All functions accepting path or file names accept both bytes and string objects, and result in an object of the same type, if a path or file name is returned. An "Availability: Unix" note means that this function is commonly found on Unix systems. It does not make any claims about its existence on a specific operating system. If not separately noted, all functions that claim "Availability: Unix" are supported on Mac OS X, which builds on a Unix core. Note All functions in this module raise None9 in the case of invalid or inaccessible file names and paths, or other arguments that have the correct type, but are not accepted by the operating system. exception None8None7¶ An alias for the built-in None6 exception. None5None4¶ The name of the operating system dependent module imported. The following names have currently been registered: None3, None2, None1,
This module never needs to be imported explicitly: the exceptions are provided in the built-in namespace as well as https://docs.python.org/2/library/exceptions.html the exceptions module. For class exceptions, in a try statement with an except clause that mentions a particular class, that clause also handles http://parenchym.com/pymblog/new-exception-hierarchy-in-python-33.html any exception classes derived from that class (but not exception classes from which it is derived). Two exception classes that are not related via subclassing are python exception never equivalent, even if they have the same name. The built-in exceptions listed below can be generated by the interpreter or built-in functions. Except where mentioned, they have an "associated value" indicating the detailed cause of the error. This may be a string or a tuple containing several items of information (e.g., an python 3 os error code and a string explaining the code). The associated value is the second argument to the raise statement. If the exception class is derived from the standard root class BaseException, the associated value is present as the exception instance's args attribute. User code can raise built-in exceptions. This can be used to test an exception handler or to report an error condition "just like" the situation in which the interpreter raises the same exception; but beware that there is nothing to prevent user code from raising an inappropriate error. The built-in exception classes can be subclassed to define new exceptions; programmers are encouraged to derive new exceptions from the Exception class or one of its subclasses, and not from BaseException. More information on defining exceptions is available in the Python Tutorial under User-defined Exceptions. The following exceptions are only used as base classes for other exceptions. exception BaseException¶ The base clas
the new exception hierarchy. Specifically, I was working on some file-related routines and found in the release notes, that for this domain a new set of exceptions is introduced and that IOError is now OSError. Things are simple for code that will only run in Python 3.3 andabove: try: open("/tmp/i_am_not_here", "r") except OSError as e: print("Caught:", e) But what if the program also must run with Python 3.2 and before? Clearly the above code will not catch the exception raised there, because it is an IOError. And IOError in the old hierarchy is a sibling of OSError. In Python 3.3, the documentation for "OSError"states: Changed in version 3.3: EnvironmentError, IOError, WindowsError, VMSError, socket.error, select.error and mmap.error have been merged into OSError. What do they mean by "have been merged into OSError"? Are IOError and OSError treated the same in Python3.3+? Yes. They are literallyidentical: Python 2.7.3 (default, Sep 9 2012, 17:41:34) [GCC 4.7.1] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> IOError == OSError False Python 3.3.0 (default, Sep 29 2012, 11:14:25) [GCC 4.7.2] on linux Type "help", "copyright", "credits" or "license" for more information. >>> IOError == OSError True So, in code that must run in Python 3.3 and versions before, we must use IOError: from __future__ import print_function try: open("/tmp/i_am_not_here", "r") except IOError as e: print("Caught:", e) Let's compare the changes in hierarchy between Python 2.7, 3.2 and3.3: Unfortunately, this depiction is not too helpful, because there is a change between Python 2.7 and 3.2 that affects almost all exceptions: In Python 2.7, all exceptions are children of StandardError, and from Python 3 on they descend directly from Exception. If we concentrate upon the exceptions, the image is clearer. Here are the changes between Python 2.7, 3.2, 3.3 and 3.4 (dev) [1] [1]I enclosed 3.4 because its documentation of OSError says "Changed in version 3.4.", but I cannot see the difference to 3.3. Dirk Makowski 26 years programming and using computers. 12 years freelance software developer, IT trainer, and consultant. Profile Available for hire Professional WebsitesParenchym 3amcode Old Blog Personal WebsiteThe Annwn social github rss feed Categories JavaScript Misc Projects Python Tech Tags requirejs bytes Python3.3 templates UI Web Site bind Tatort JavaScript Multiprocessing Pelican elFinder file manager StringIO unicode Profiling feedgenerator Python Concurrency funny Testing 2