Python
Errors in Python: Syntax, Runtime and Logical
Three kinds of error, found at three different moments. Only one of them can be caught, and the one that catches nobody out is the most dangerous.
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Python
try, except, else and finally
try runs risky code, except handles a failure, else runs when nothing failed, and finally always runs. Each block has one job and using the wrong one...
Python
The Exception Hierarchy
Every exception is a class in one inheritance tree. Catching a parent catches all its children, which is what makes handler order and handler width ma...
Python
raise and Custom Exceptions
raise signals a failure your own code has detected. A custom exception class gives that failure a name callers can catch precisely.
Python
Reading and Writing Text Files
open() gives you a file object, with reads a file object safely, and four methods cover every text file you will ever process.
Python
File Modes and Context Managers
The mode string decides whether a file is read, written, appended or created, and whether it is treated as text or bytes. The with statement makes any...
Python
Binary Files, seek and tell
Binary mode gives you the raw bytes, and seek and tell let you move around inside a file instead of reading it from start to finish.
Python
Paths and Directories with pathlib
pathlib turns file paths into objects with methods. It replaces string joining and most of os.path, and it works the same on Windows, macOS and Linux.
Python
Modules and the import Statement
A module is a .py file. import runs it once, caches it, and binds a name. Every import form is a variation on those three steps.
Python
__name__, __main__ and Running Modules
Every module has a __name__. It is "__main__" when the file is run directly and the module name when it is imported, which is what the main guard test...
Python
Packages and __init__.py
A package is a directory of modules. __init__.py marks it and defines its public face, and relative imports let modules inside it find each other.
Python
Numbers: math, random, statistics, decimal and fractions
Five standard library modules cover every numeric need core Python has: exact maths, randomness, summary statistics, exact decimals and exact fraction...