You need to double the {{ and }}: >>> x = ” {{ Hello }} {0} ” >>> print(x.format(42)) ‘ { Hello } 42 ‘ Here’s the relevant part of the Python documentation for format string syntax: Format strings contain “replacement fields” surrounded by curly braces {}. Anything that is not contained in braces is … Read more
You are running into the old problem with floating point numbers that not all numbers can be represented exactly. The command line is just showing you the full floating point form from memory. With floating point representation, your rounded version is the same number. Since computers are binary, they store floating point numbers as an … Read more
The len() function can be used with several different types in Python – both built-in types and library types. For example: >>> len([1, 2, 3]) 3
Note: This answer was intended for a very specific question. For most programmers coming here from a search engine, this is not the answer you are looking for. Typically you would structure your files into packages (see other answers) instead of modifying the search path. By default, you can’t. When importing a file, Python only … Read more
Use random.choice(): import random foo = [‘a’, ‘b’, ‘c’, ‘d’, ‘e’] print(random.choice(foo)) For cryptographically secure random choices (e.g., for generating a passphrase from a wordlist), use secrets.choice(): import secrets foo = [‘battery’, ‘correct’, ‘horse’, ‘staple’] print(secrets.choice(foo)) secrets is new in Python 3.6. On older versions of Python you can use the random.SystemRandom class: import random … Read more
Try hasattr(): if hasattr(a, ‘property’): a.property See zweiterlinde’s answer below, who offers good advice about asking forgiveness! A very pythonic approach! The general practice in python is that, if the property is likely to be there most of the time, simply call it and either let the exception propagate, or trap it with a try/except … Read more
Usually, activating a virtualenv gives you a shell function named: $ deactivate which puts things back to normal. I have just looked specifically again at the code for virtualenvwrapper, and, yes, it too supports deactivate as the way to escape from all virtualenvs. If you are trying to leave an Anaconda environment, the command depends … Read more
Given a module foo with method bar: import foo bar = getattr(foo, ‘bar’) result = bar() getattr can similarly be used on class instance bound methods, module-level methods, class methods… the list goes on.
In Python 3, you can use the sep= and end= parameters of the print function: To not add a newline to the end of the string: print(‘.’, end=”) To not add a space between all the function arguments you want to print: print(‘a’, ‘b’, ‘c’, sep=”) You can pass any string to either parameter, and … Read more
Variables declared inside the class definition, but not inside a method are class or static variables: >>> class MyClass: … i = 3 … >>> MyClass.i 3 As @millerdev points out, this creates a class-level i variable, but this is distinct from any instance-level i variable, so you could have >>> m = MyClass() >>> … Read more