2nd Python Bootcamp IAG - Basics II

Transcript

1. Python Bootcamp An(other) Python Introduction II PhD Bruno C. Quint bquint@ctio.noao.edu Resident Astronomer at SOAR Telescope
2. Table of Contents § What is Python? § What will you need? § Python as a terminal § Python as a script § Types of variables § Loops and Control § Using Methods and Libs § Gathering Information
3. 3 if/elif/else fruit = ‘banana’ if fruit is ‘apple’: ....eat_it() elif fruit is ‘orange’: ....make_a_juice() else: ....leave_it() Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html
4. 4 if/elif/else fruit = ‘banana’ if fruit is ‘apple’: ....eat_it() elif fruit is ‘orange’: ....make_a_juice() else: ....leave_it() Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html
5. 5 Python relies on identation, so DON’T MESS UP! if/elif/else Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html fruit = ‘banana’ if fruit is ‘apple’: ....eat_it() elif fruit is ‘orange’: .....make_a_juice() else: ....leave_it()
6. 6 if/elif/else Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html PEP8 HIGHLY recommends you to use 4 spaces. And NEVER mix spaces and tabs. For more informations, read the PEP-8. fruit = ‘banana’ if fruit is ‘apple’: ....eat_it() elif fruit is ‘orange’: ....make_a_juice() else: ....leave_it()
7. 7 if/elif/else fruit = ‘banana’ if fruit is ‘apple’: ....eat_it() elif fruit is ‘orange’: ....make_a_juice() else: ....leave_it() Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html
8. 8 if/elif/else Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html fruit = ‘banana’ if fruit == ‘apple’: ....eat_it() elif fruit == ‘orange’: ....make_a_juice() else: ....leave_it()
9. >>> my_list = [‘a’, ‘b’, ‘c’] >>> >>> for my_item in my_list: ....print my_item .... a b c 9 for Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html List, tuples, arrays, matrixes, dictionaries
10. >>> my_list = [‘a’, ‘b’, ‘c’] >>> >>> for my_item in my_list: ....print my_item .... a b c 10 for Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html List, tuples, arrays, matrixes, dictionaries
11. >>> my_list = [‘a’, ‘b’, ‘c’] >>> >>> for index in range(len(my_list)): ....print index, my_list[index] .... 0 a 1 b 2 c 11 for Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html List, tuples, arrays, matrixes, dictionaries Using indexes
12. >>> my_list = [‘a’, ‘b’, ‘c’] >>> >>> for index in range(len(my_list)): ....print index, my_list[index] .... 0 a 1 b 2 c 12 for Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html List, tuples, arrays, matrixes, dictionaries Using indexes len(x) → return the number of elements of x.
13. >>> my_list = [‘a’, ‘b’, ‘c’] >>> >>> for index in range(3): ....print index, my_list[index] .... 0 a 1 b 2 c 13 for Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html List, tuples, arrays, matrixes, dictionaries Using indexes len(x) → return the number of elements of x.
14. >>> my_list = [‘a’, ‘b’, ‘c’] >>> >>> for index in range(3): ....print index, my_list[index] .... 0 a 1 b 2 c 14 for Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html List, tuples, arrays, matrixes, dictionaries Using indexes range(n) → return a list with n integers starting at 0.
15. >>> my_list = [‘a’, ‘b’, ‘c’] >>> >>> for index in [0, 1, 2]: ....print index, my_list[index] .... 0 a 1 b 2 c 15 for Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html List, tuples, arrays, matrixes, dictionaries Using indexes range(n) → return a list with n integers starting at 0.
16. >>> while some_condition_is_true: ....do_something() 16 while Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html
17. test_while.py >>> n_interested = 5 >>> >>> while n_interested < 0: ....print(“ #Success :D ”) ....n_interested = n_interested - 1 .... >>> print(“ #Fail :( ”) 17 while Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html
18. test_while.py 18 while Loops and control 13/02/2017 Python Bootcamp – An(other) Python introduction II More at https://docs.python.org/2/tutorial/controlflow.html >>> n_interested = 5 >>> >>> while n_interested < 0: ....print(“ #Success :D ”) ....n_interested = n_interested - 1 .... >>> print(“ #Fail :( ”) $ python foo.py #Success :D #Success :D #Success :D #Success :D #Success :D #Fail :(
19. Methods Defining your own 19 >>> def my_method(x, y): ....“““Add here some description””” ....k = 2 * x - y ....return k More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II Define a method
20. Methods Defining your own 20 >>> def my_method(x, y): ....“““Add here some description””” ....k = 2 * x - y ....return k .... >>> my_method(2, 4) 0 More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II Define a method x and y are required parameters.
21. Methods Defining your own 21 Define a method x and y are now keyword parameters. >>> def my_method(x, y): ....“““Add here some description””” ....k = 2 * x - y ....return k .... >>> my_method(y=4, x=2) 0 More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II
22. Methods Defining your own 22 Define a method z and w are now default parameters. >>> def my_method(x, y, z=1, w=0): ....“““Add here some description””” ....k = 2 * x - y / z + w ....return k .... >>> my_method(y=4, x=2) 0 More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II
23. >>> def my_method(x, y, z=1, w=0): ....“““Add here some description””” ....k = 2 * x - y / z + w ....return k .... >>> my_method(y=4, x=2) 0 Methods Defining your own 23 Define a method z and w are now default parameters. More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II Default parameters have default values.
24. Methods Defining your own 24 Define a method z and w are now default parameters. >>> def my_method(x, y, z=1, w=0): ....“““Add here some description””” ....k = 2 * x - y / z + w ....return k .... >>> my_method(y=4, x=2, w=5) 5 More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II
25. Methods Defining your own 25 Watch out namespaces! >>> >>> def my_method(x, y): ....“““Add here some description””” ....k = 2 * x - y ....return k .... >>> my_method(2, 4) 0 More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II
26. Methods Defining your own 26 Watch out namespaces! >>> >>> def my_method(x, y): ....“““Add here some description””” ....k = 2 * x - y ....return k .... >>> my_method(4) More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II
27. Methods Defining your own 27 Watch out namespaces! >>> >>> def my_method(x, y): ....“““Add here some description””” ....k = 2 * x - y ....return k .... >>> my_method(4) NameError: global name 'x' is not defined More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II
28. Methods Defining your own 28 Watch out namespaces! >>> x = 2 >>> def my_method(x, y): ....“““Add here some description””” ....k = 2 * x - y ....return k .... >>> my_method(4) 0 More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II
29. Methods Defining your own 29 Watch out namespaces! >>> >>> def my_method(x, y): ....“““Add here some description””” ....k = 2 * x - y ....return k .... >>> x = 2 >>> my_method(4) 0 More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II
30. Methods Defining your own 30 Watch out namespaces! >>> x = 2 >>> def my_method(x, y): ....“““Add here some description””” ....k = 2 * x - y ....return k .... >>> my_method(3, 4) More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II
31. Methods Defining your own 31 Watch out namespaces! >>> x = 2 >>> def my_method(x, y): ....“““Add here some description””” ....k = 2 * x - y ....return k .... >>> my_method(3, 4) 2 More on methods (Functions): Here 13/02/2017 Python Bootcamp – An(other) Python introduction II
32. 32 >>> X = 2 >>> my_method = lambda x, y: 2 * x – y >>> >>> my_method(3, 4) 2 Use lambda! More on methods (Functions): Here Methods Defining your own 13/02/2017 Python Bootcamp – An(other) Python introduction II
33. 13/10/2015 Python Bootcamp - Basic I 33 foo.py 01 def my_method(x, y): 02 ....“““Some description””” 03 ....k = 2 * x - y 04 ....return k 05 06 print my_method(3, 4) More on methods (Functions): Here Methods Defining your own Re-using your functions
34. 13/10/2015 Python Bootcamp - Basic I 34 foo.py 01 import foo 02 foo.my_method(5, 2) use.py 01 def my_method(x, y): 02 ....“““Some description””” 03 ....k = 2 * x - y 04 ....return k 05 06 print my_method(3, 4) More on methods (Functions): Here Methods Defining your own Re-using your functions
35. 13/10/2015 Python Bootcamp - Basic I 35 foo.py 01 def my_method(x, y): 02 ....“““Some description””” 03 ....k = 2 * x - y 04 ....return k 05 06 print my_method(3, 4) More on methods (Functions): Here Methods Defining your own Re-using your functions 01 import foo 02 foo.my_method(5, 2) use.py $ python use.py 2 8
36. 13/10/2015 Python Bootcamp - Basic I 36 foo.py 01 def my_method(x, y): 02 ....“““Some description””” 03 ....k = 2 * x - y 04 ....return k 05 06 07 print my_method(3, 4) More on methods (Functions): Here Methods Defining your own Re-using your functions 01 import foo 02 foo.my_method(5, 2) use.py $ python use.py 8
37. 13/10/2015 Python Bootcamp - Basic I 37 foo.py 01 def my_method(x, y): 02 ....“““Some description””” 03 ....k = 2 * x - y 04 ....return k 05 06 if __name__ == ‘__main__’: 07 print my_method(3, 4) More on methods (Functions): Here Methods Defining your own Re-using your functions 01 import foo 02 foo.my_method(5, 2) use.py $ python use.py 8
38. 13/10/2015 Python Bootcamp - Basic I 38 foo.py 01 def my_method(x, y): 02 ....“““Some description””” 03 ....k = 2 * x - y 04 ....return k 05 06 if __name__ == ‘__main__’: 07 ....print my_method(3, 4) More on methods (Functions): Here Methods Defining your own Re-using your functions 01 import foo 02 foo.my_method(5, 2) use.py $ python use.py 8
39. 39 Methods Using yours >>> len(‘Hello World!’) 12 >>> range(5) [0, 1, 2, 3, 4] >>> type(‘Aloha!’) <type ‘string’> >>> abs(-5.3) 5.3 Built-in methods (or Functions) Check all the build-in functions at https://docs.python.org/2/library/functions.html 13/02/2017 Python Bootcamp – An(other) Python introduction II
40. 40 >>> import math >>> math.sqrt(9) 3 Using methods from libs For more, check: https://docs.python.org/2/tutorial/modules.html Methods Using yours 13/02/2017 Python Bootcamp – An(other) Python introduction II
41. 41 >>> import math >>> math.sqrt(9) 3 >>> import math as m >>> m.sqrt(9) 3 Using methods from libs For more, check: https://docs.python.org/2/tutorial/modules.html Methods Using yours 13/02/2017 Python Bootcamp – An(other) Python introduction II
42. 42 >>> from math import sqrt, log >>> sqrt(9) 3 >>> log(10) 1 Using methods from libs For more, check: https://docs.python.org/2/tutorial/modules.html Methods Using yours 13/02/2017 Python Bootcamp – An(other) Python introduction II
43. 43 >>> from math import * >>> sqrt(9) 3 >>> log(10) 1 Using methods from libs For more, check: https://docs.python.org/2/tutorial/modules.html Methods Using yours 13/02/2017 Python Bootcamp – An(other) Python introduction II
44. 44 >>> from math import * >>> from numpy import * >>> sqrt(9) 3 >>> x = array([1, 4, 9]) >>> sqrt(x) [1, 2, 3] Using methods from libs For more, check: https://docs.python.org/2/tutorial/modules.html Methods Using yours 13/02/2017 Python Bootcamp – An(other) Python introduction II
45. 45 >>> from numpy import * >>> from math import * >>> sqrt(9) 3 >>> x = array([1, 4, 9]) >>> sqrt(x) TypeError: only length-1 arrays can be converted to Python scalars Using methods from libs For more, check: https://docs.python.org/2/tutorial/modules.html Methods Using yours 13/02/2017 Python Bootcamp – An(other) Python introduction II
46. 46 >>> from math import sqrt as msqrt >>> from numpy import sqrt as nsqrt >>> msqrt(9) 3. >>> nsqrt([1, 4, 9]) [1., 2., 3.] Using methods from libs For more, check: https://docs.python.org/2/tutorial/modules.html Methods Using yours 13/02/2017 Python Bootcamp – An(other) Python introduction II
47. 47 >>> s = ‘Hello World!’ >>> s.lower() ‘hello world!’ >>> s.isdigit() False Using methods from objects For more, check: https://docs.python.org/2/tutorial/modules.html Methods Using yours 13/02/2017 Python Bootcamp – An(other) Python introduction II
48. 48 Gathering information >>> def double(x): >>> ....“““Doubles the value of x””” >>> ....return 2 * x >>> The built-in function help() Help on built-in function help() here. 13/02/2017 Python Bootcamp – An(other) Python introduction II
49. 49 Gathering information The built-in function help() >>> help(double_value) Help on function double_value: double_value(x) Return the double of x Help on built-in function help() here. 13/02/2017 Python Bootcamp – An(other) Python introduction II
50. 50 Gathering information >>> y = 3. >>> help(y) Help on float object: class float(object) | float(x) -> floating point number | | Convert a string or number to a floating point | number, if possible. ... The built-in function help() Help on built-in function help() here. 13/02/2017 Python Bootcamp – An(other) Python introduction II
51. 51 Gathering information >>> y = 3. >>> help(y) The built-in function help() >>> z = 3 >>> help(z) >>> s = ‘a string’ >>> help(s) Help on built-in function help() here. 13/02/2017 Python Bootcamp – An(other) Python introduction II
52. 52 >>> y = 3. >>> dir(y) ['__abs__', '__add__', ..., 'is_integer', 'real'] The built-in function dir() Help on built-in function dir() here. Gathering information 13/02/2017 Python Bootcamp – An(other) Python introduction II
53. 53 >>> y = 3. >>> dir(y) ['__abs__', '__add__', ..., 'is_integer', 'real'] The built-in function dir() >>> y = 3 >>> dir(y) ['__abs__', '__add__', ..., ‘real', ‘to_bytes'] Help on built-in function dir() here. Gathering information 13/02/2017 Python Bootcamp – An(other) Python introduction II
54. 54 >>> y = 3. >>> dir(y) ['__abs__', '__add__', ..., 'is_integer', 'real'] The built-in function dir() ._variable is semiprivate and meant just for convention .__variable is considered superprivate and gets namemangled to prevent accidental access .__variable__ is typically reserved for builtin methods or variables Help on built-in function dir() here. Gathering information 13/02/2017 Python Bootcamp – An(other) Python introduction II
55. Questions? 55 13/02/2017 Python Bootcamp – An(other) Python introduction II