![str (continuation)
๏ต Indexing elements: x[0] is the first element, x[1] is the second, and so on
๏ต Slicing:
๏ต [start:end:step]
๏ต [start:] # end is the length of the sequence, step assumed to be 1
๏ต [:end] # start is the beginning of the sequence, step assumed to be 1
๏ต [::step] # start is the beginning of the sequence, end is the length
๏ต [start::step]
๏ต [:end:step]
๏ต These operations are common for all sequence types](https://image.slidesharecdn.com/introductionpart1-160906115340/85/Introduction-to-the-basics-of-Python-programming-part-1-13-320.jpg)
![list
๏ต x = [] # empty list
๏ต x = [1, 2, 3] # list with 3 elements
๏ต x = list(โHelloโ)
๏ต x.append(โsomethingโ) # append object to the end of the list
๏ต x.insert(2, โsomethingโ) # append object before index 2](https://image.slidesharecdn.com/introductionpart1-160906115340/85/Introduction-to-the-basics-of-Python-programming-part-1-17-320.jpg)
![Control Flow: for loop (continuation)
colors = [โredโ, โgreenโ, โblueโ, โorangeโ]
for color in colors:
print(color)
colors = [[1, โredโ], [2, โgreenโ], [3, โblueโ], [4, โorangeโ]]
for i, color in colors:
print(i, โ ---> โ, color)](https://image.slidesharecdn.com/introductionpart1-160906115340/85/Introduction-to-the-basics-of-Python-programming-part-1-20-320.jpg)
![Challenge
๏ต Rewrite the following code using enumerate and the following list of colors:
[โredโ, โgreenโ, โblueโ, โorangeโ] .
(hint: help(enumerate))
colors = [[1, โredโ], [2, โgreenโ], [3, โblueโ], [4, โorangeโ]]
for i, color in colors:
print(i, โ ---> โ, color)](https://image.slidesharecdn.com/introductionpart1-160906115340/85/Introduction-to-the-basics-of-Python-programming-part-1-22-320.jpg)
![Control Flow: for loop (continuation)
colors = [โredโ, โgreenโ, โorangeโ, โblueโ]
for color in colors:
print(color)
else:
print(โDone!โ)](https://image.slidesharecdn.com/introductionpart1-160906115340/85/Introduction-to-the-basics-of-Python-programming-part-1-24-320.jpg)
![Control Flow: break and (continue)
colors = [โredโ, โgreenโ, โblueโ, โpurpleโ, โorangeโ]
for color in colors:
if len(color) > 5:
break
else:
print(color)](https://image.slidesharecdn.com/introductionpart1-160906115340/85/Introduction-to-the-basics-of-Python-programming-part-1-29-320.jpg)
Introduction to the basics of Python programming (part 1)
- 1. Introduction to the basics of Python programming (PART 1) by Pedro Rodrigues ([email protected])
- 2. A little about me ๏ต Name: Pedro Rodrigues ๏ต Origin: Luanda (Angola) ๏ต In the Netherlands since 2013 ๏ต Former CTO and Senior Backend Engineer ๏ต Freelance Software Engineer ๏ต Book author: Start a Career with Python ๏ต Coach
- 3. Why this Meetup Group? ๏ต Promote the usage of Python ๏ต Gather people from different industries and backgrounds ๏ต Teach and Learn
- 4. What will be covered ๏ต First steps with the interactive shell: CPython ๏ต Variables and Data types ๏ต Single and Multi variable assignment ๏ต Immutable: strings, tuples, bytes, frozensets ๏ต Mutable: lists, bytearrays, sets, dictionaries ๏ต Control Flow ๏ต if statement ๏ต for statement ๏ต Range, Iterable and Iterators ๏ต while statement ๏ต break and continue
- 5. What is Python? ๏ต Dutch product: create by Guido van Rossum in the late 80s ๏ต Interpreted language ๏ต Multi-paradigm: Procedural (imperative), Object Oriented, Functional ๏ต Dynamically Typed
- 6. Python interpreter ๏ต CPython: reference, written in C ๏ต PyPy, Jython, IronPython ๏ต help() ๏ต dir()
- 8. Variables ๏ต Binding between a name and an object ๏ต Single variable assignment: x = 1 ๏ต Multi variable assignment: x, y = 1, 2 ๏ต Swap values: x, y = y, x
- 9. Data Types ๏ต Numbers: int (Integers), float (Real Numbers), bool (Boolean, a subset of int) ๏ต Immutable Types: str (string), tuple, bytes, frozenset ๏ต Mutable Types: list, set, bytearray, dict (dictionary) ๏ต Sequence Types: str, tuple, bytes, bytearray, list ๏ต Determining the type of an object: type()
- 10. Numbers: int and float ๏ต 1 + 2 (addition) ๏ต 1 โ 2 (subtraction) ๏ต 1 * 2 (multiplication) ๏ต 1 / 2 (division) ๏ต 1 // 2 (integer or floor division) ๏ต 3 % 2 (modulus or remainder of the division) ๏ต 2**2 (power)
- 11. Numbers: bool (continuation) ๏ต 1 > 2 ๏ต 1 < 2 ๏ต 1 == 2 ๏ต Boolean operations: and, or, not ๏ต Objects can also be tested for their truth value. The following values are false: None, False, zero of any numeric type, empty sequences, empty mapping
- 12. str (String) ๏ต x = โThis is a stringโ ๏ต x = โThis is also a stringโ ๏ต x = โโโSo is this oneโโโ ๏ต x = โโโAnd this one as wellโโโ ๏ต x = โโโ This is a string that spans more than one line. This can also be used for comments. โโโ
- 13. str (continuation) ๏ต Indexing elements: x[0] is the first element, x[1] is the second, and so on ๏ต Slicing: ๏ต [start:end:step] ๏ต [start:] # end is the length of the sequence, step assumed to be 1 ๏ต [:end] # start is the beginning of the sequence, step assumed to be 1 ๏ต [::step] # start is the beginning of the sequence, end is the length ๏ต [start::step] ๏ต [:end:step] ๏ต These operations are common for all sequence types
- 14. str (continuation) ๏ต Some common string methods: ๏ต join (concatenates the strings from an iterable using the string as glue) ๏ต format (returns a formatted version of the string) ๏ต strip (returns a copy of the string without leading and trailing whitespace) ๏ต Use help(str.<command>) in the interactive shell and dir(str)
- 15. Control Flow (pt. 1): if statement ๏ต Compound statement if <expression>: suite elif <expression2>: suite else: suite
- 16. Control Flow (pt. 2): if statement age = int(input(โ> โ)) if age >= 30: print(โYou are 30 or aboveโ) elif 20 < age < 30: print(โYou are in your twentiesโ) else: print(โYou are less than 20โ)
- 17. list ๏ต x = [] # empty list ๏ต x = [1, 2, 3] # list with 3 elements ๏ต x = list(โHelloโ) ๏ต x.append(โsomethingโ) # append object to the end of the list ๏ต x.insert(2, โsomethingโ) # append object before index 2
- 18. dict (Dictionaries) ๏ต Mapping between keys and values ๏ต Values can be of whatever type ๏ต Keys must be hashable ๏ต x = {} # empty dictionary ๏ต x = {โNameโ: โJohnโ, โAgeโ: 23} ๏ต x.keys() ๏ต x.values() ๏ต x.items()
- 19. Control Flow: for loop ๏ต Also compound statement ๏ต Iterates over the elements of an iterable object for <target> in <expression>: suite else: suite
- 20. Control Flow: for loop (continuation) colors = [โredโ, โgreenโ, โblueโ, โorangeโ] for color in colors: print(color) colors = [[1, โredโ], [2, โgreenโ], [3, โblueโ], [4, โorangeโ]] for i, color in colors: print(i, โ ---> โ, color)
- 21. Control Flow: for loop (continuation) ๏ต Iterable is a container object able to return its elements one at a time ๏ต Iterables use iterators to return their elements one at a time ๏ต Iterator is an object that represents a stream of data ๏ต Must implement two methods: __iter__ and __next__ (Iterator protocol) ๏ต Raises StopIteration when elements are exhausted ๏ต Lazy evaluation
- 22. Challenge ๏ต Rewrite the following code using enumerate and the following list of colors: [โredโ, โgreenโ, โblueโ, โorangeโ] . (hint: help(enumerate)) colors = [[1, โredโ], [2, โgreenโ], [3, โblueโ], [4, โorangeโ]] for i, color in colors: print(i, โ ---> โ, color)
- 23. Control Flow: for loop (continuation) ๏ต range: represents a sequence of integers ๏ต range(stop) ๏ต range(start, stop) ๏ต range(start, stop, step)
- 24. Control Flow: for loop (continuation) colors = [โredโ, โgreenโ, โorangeโ, โblueโ] for color in colors: print(color) else: print(โDone!โ)
- 25. Control Flow: while loop ๏ต Executes the suite of statements as long as the expression evaluates to True while <expression>: suite else: suite
- 26. Control Flow: while loop (continuation) counter = 5 while counter > 0: print(counter) counter = counter - 1 counter = 5 while counter > 0: print(counter) counter = counter โ 1 else: print(โDone!โ)
- 27. Challenge ๏ต Rewrite the following code using a for loop and range: counter = 5 while counter > 0: print(counter) counter = counter - 1
- 28. Control Flow: break and continue ๏ต Can only occur nested in a for or while loop ๏ต Change the normal flow of execution of a loop: ๏ต break stops the loop ๏ต continue skips to the next iteration for i in range(10): if i % 2 == 0: continue else: print(i)
- 29. Control Flow: break and (continue) colors = [โredโ, โgreenโ, โblueโ, โpurpleโ, โorangeโ] for color in colors: if len(color) > 5: break else: print(color)
- 30. Challenge ๏ต Rewrite the following code without the if statement (hint: use the step in range) for i in range(10): if i % 2 == 0: continue else: print(i)
- 31. Reading material ๏ต Data Model (Python Language Reference): https://docs.python.org/3/reference/datamodel.html ๏ต The if statement (Python Language Reference): https://docs.python.org/3/reference/compound_stmts.html#the-if-statement ๏ต The for statement (Python Language Reference): https://docs.python.org/3/reference/compound_stmts.html#the-for-statement ๏ต The while statement (Python Language Reference): https://docs.python.org/3/reference/compound_stmts.html#the-while-statement
- 32. More resources ๏ต Python Tutorial: https://docs.python.org/3/tutorial/index.html ๏ต Python Language Reference: https://docs.python.org/3/reference/index.html ๏ต Slack channel: https://startcareerpython.slack.com/ ๏ต Start a Career with Python newsletter: https://www.startacareerwithpython.com/ ๏ต Book 15% off (NZ6SZFBL): https://www.createspace.com/6506874
- 33. set ๏ต Unordered mutable collection of elements ๏ต Doesnโt allow duplicate elements ๏ต Elements must be hashable ๏ต Useful to test membership ๏ต x = set() # empty set ๏ต x = {1, 2, 3} # set with 3 integers ๏ต 2 in x # membership test
- 34. tuple ๏ต x = 1, ๏ต x = (1,) ๏ต x = 1, 2, 3 ๏ต x = (1, 2, 3) ๏ต x = (1, โHello, world!โ) ๏ต You can also slice tuples
- 35. bytes ๏ต Immutable sequence of bytes ๏ต Each element is an ASCII character ๏ต Integers greater than 127 must be properly escaped ๏ต x = bโThis is a bytes objectโ ๏ต x = bโThis is also a bytes objectโ ๏ต x = bโโโSo is thisโโโ ๏ต x = bโโโor even thisโโโ
- 36. bytearray ๏ต Mutable counterpart of bytes ๏ต x = bytearray() ๏ต x = bytearray(10) ๏ต x = bytearray(bโHello, world!โ)