Python 101 Day 2

Transcript

1. PYTHON 101
2. What is Python? ▪ Interpreted Language – don't have to compile it ▪ Multi-paradigm: OOP (no access specifiers), Functional and others... ▪ Guido van Rossum ("Benevolent Dictator For Life") ▪ Dynamic typing – Don't have to specify data types for variables ▪ Pythonic code and Zen of Python ▪ Cython, PyPy ▪ Indentation ▪ Built in garbage collector
3. Built in types ▪ Immutable built-in types of Python – Numbers – Strings – Tuples ▪ Mutable built-in types of Python – List – Dictionaries – Sets
4. Built in functions ▪ range([start], stop[, step]) ▪ sorted ▪ reversed ▪ And many more...
5. Examine ▪ type() ▪ dir() ▪ id() ▪ help()
6. Variables ▪ Local ▪ Global
7. Comments ▪ # ▪ ''' '''
8. Assignments = ▪ x = 2 ▪ C/C++: "typed variable name x receives a copy of numeric value 2". The (right-hand) value is copied into an allocated storage location for which the (left-hand) variable name is the symbolic address. ▪ Python: "(generic) name x receives a reference to a separate, dynamically allocated object of numeric (int) type of value 2."
9. Copies ▪ Deep – Nested Structures ▪ Shallow
10. Let's do some maths! ▪ // vs / ▪ ** ▪ Results of a division is always a float ▪ 1 is True 0 is False ▪ Is 2 True?
11. Comparisons ▪ == vs is (content vs type) ▪ and, or, not ▪ Can be chained
12. Strings ▪ "{} is {}".format("Sun", "hot") ▪ Can't change a string ▪ Try to avoid +
13. If else ▪ x if c else y ▪ elif ▪ Pass ▪ No switches
14. while n = 5 while(n > 0): print(n) n -= 1
15. Lists ▪ append, pop, remove, insert, index, extend ▪ Slicing ▪ :: ▪ list[start:end:step] ▪ join ▪ List comprehensions ▪ [:] deep copy ▪ in
16. for ▪ Calls iter() on object ▪ range – values on demand for x in range(0, 10, 1): print(x)
17. Any and All ▪ Any returns True if any one item in the iterable is True ▪ All returns True if all the items in the iterable is True
18. We do have arrays... ▪ Array ▪ Have to be of a specific type ▪ https://www.python.org/doc/essays/list2str/
19. Tuple ▪ Immutable ▪ Unpacking and swapping ▪ Initialization ▪ a, b = 1, 2
20. Dictionary ▪ What keys are hashable? ▪ get(), setdefault() ▪ Dict comprehensions ▪ {x: x+2 for x in range(1,100)}
21. def ▪ Functions are first class objects – I can assign them to variables ▪ Pass by value vs pass by reference??? ▪ *args – Variable number of args ▪ **kwargs – Variable number of keyword args
22. Magic methods ▪ Overloaded operators in C++ ▪ What if I want to compare two objects with < and > ? ▪ object.__lt__(self, other)
23. Maps and filters ▪ map(function, data) ▪ filter(function, data) ▪ Reduce - from functools import reduce – You need two args in the lambda
24. Try except ▪ Else – Runs only if no exceptions were raised ▪ Finally – Run everytime ▪ raise
25. Sets ▪ Elements of set have to be immutable ▪ No order ▪ & | - >= <= ▪ {x for x in range(1,100)}
26. class ▪ First class objects ▪ Self - myobject.method(arg1, arg2) => MyClass.method(myobject, arg1, arg2) ▪ Hidden variables – Not really hidden ▪ Supports Multiple inheritance ▪ Isinstance ▪ issubclass
27. ▪ Generators ▪ Iterators ▪ Closures ▪ Decorators
28. Feedback! ▪ http://bit.ly/2Awy91c