diff options
Diffstat (limited to 'python3.html.markdown')
| -rw-r--r-- | python3.html.markdown | 57 |
1 files changed, 42 insertions, 15 deletions
diff --git a/python3.html.markdown b/python3.html.markdown index c7fbf342..ef78ce37 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -41,10 +41,10 @@ Note: This article applies to Python 3 specifically. Check out [here](http://lea 10 * 2 # => 20 35 / 5 # => 7.0 -# Result of integer division truncated down both for positive and negative. +# Integer division rounds down for both positive and negative numbers. 5 // 3 # => 1 -5.0 // 3.0 # => 1.0 # works on floats too -5 // 3 # => -2 +5.0 // 3.0 # => 1.0 # works on floats too -5.0 // 3.0 # => -2.0 # The result of division is always a float @@ -72,15 +72,24 @@ not False # => True True and False # => False False or True # => True -# Note using Bool operators with ints -# False is 0 and True is 1 +# True and False are actually 1 and 0 but with different keywords +True + True # => 2 +True * 8 # => 8 +False - 5 # => -5 + +# Comparison operators look at the numerical value of True and False +0 == False # => True +1 == True # => True +2 == True # => False +-5 != False # => True + +# Using boolean logical operators on ints casts them to booleans for evaluation, but their non-cast value is returned # Don't mix up with bool(ints) and bitwise and/or (&,|) +bool(0) # => False +bool(4) # => True +bool(-6) # => True 0 and 2 # => 0 -5 or 0 # => -5 -0 == False # => True -2 == True # => False -1 == True # => True --5 != False != True #=> True # Equality is == 1 == 1 # => True @@ -96,7 +105,10 @@ False or True # => True 2 <= 2 # => True 2 >= 2 # => True -# Comparisons can be chained! +# Seeing whether a value is in a range +1 < 2 and 2 < 3 # => True +2 < 3 and 3 < 2 # => False +# Chaining makes this look nicer 1 < 2 < 3 # => True 2 < 3 < 2 # => False @@ -143,7 +155,7 @@ len("This is a string") # => 16 name = "Reiko" f"She said her name is {name}." # => "She said her name is Reiko" # You can basically put any Python statement inside the braces and it will be output in the string. -f"{name} is {len(name)} characters long." +f"{name} is {len(name)} characters long." # => "Reiko is 5 characters long." # None is an object @@ -302,16 +314,19 @@ valid_dict = {(1,2,3):[1,2,3]} # Values can be of any type, however. filled_dict["one"] # => 1 # Get all keys as an iterable with "keys()". We need to wrap the call in list() -# to turn it into a list. We'll talk about those later. Note - Dictionary key -# ordering is not guaranteed. Your results might not match this exactly. -list(filled_dict.keys()) # => ["three", "two", "one"] +# to turn it into a list. We'll talk about those later. Note - for Python +# versions <3.7, dictionary key ordering is not guaranteed. Your results might +# not match the example below exactly. However, as of Python 3.7, dictionary +# items maintain the order at which they are inserted into the dictionary. +list(filled_dict.keys()) # => ["three", "two", "one"] in Python <3.7 +list(filled_dict.keys()) # => ["one", "two", "three"] in Python 3.7+ # Get all values as an iterable with "values()". Once again we need to wrap it # in list() to get it out of the iterable. Note - Same as above regarding key # ordering. -list(filled_dict.values()) # => [3, 2, 1] - +list(filled_dict.values()) # => [3, 2, 1] in Python <3.7 +list(filled_dict.values()) # => [1, 2, 3] in Python 3.7+ # Check for existence of keys in a dictionary with "in" "one" in filled_dict # => True @@ -447,8 +462,19 @@ prints: """ for i in range(4, 8, 2): print(i) + """ +To loop over a list, and retrieve both the index and the value of each item in the list +prints: + 0 dog + 1 cat + 2 mouse +""" +list = ["dog", "cat", "mouse"] +for i, value in enumerate(list): + print(i, value) +""" While loops go until a condition is no longer met. prints: 0 @@ -793,6 +819,7 @@ class Superhero(Human): # add additional class attributes: self.fictional = True self.movie = movie + # be aware of mutable default values, since defaults are shared self.superpowers = superpowers # The "super" function lets you access the parent class's methods |