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remove overly long lines by edit of content
Light rephrasing to stay within the constraint of 80 chars/line. The cross links at the end of the document are not affected.
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@ -155,10 +155,10 @@ b == a # => True, a's and b's objects are equal
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# You can find the length of a string
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len("This is a string") # => 16
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# You can also format using f-strings or formatted string literals (in Python 3.6+)
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# Since Python 3.6, you can use f-strings or formatted string literals.
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name = "Reiko"
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f"She said her name is {name}." # => "She said her name is Reiko"
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# You can basically put any Python expression inside the braces and it will be output in the string.
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# Any valid Python expression inside these braces is returned to the string.
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f"{name} is {len(name)} characters long." # => "Reiko is 5 characters long."
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# None is an object
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@ -297,7 +297,7 @@ filled_dict = {"one": 1, "two": 2, "three": 3}
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# Note keys for dictionaries have to be immutable types. This is to ensure that
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# the key can be converted to a constant hash value for quick look-ups.
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# Immutable types include ints, floats, strings, tuples.
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invalid_dict = {[1,2,3]: "123"} # => Raises a TypeError: unhashable type: 'list'
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invalid_dict = {[1,2,3]: "123"} # => Yield a TypeError: unhashable type: 'list'
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valid_dict = {(1,2,3):[1,2,3]} # Values can be of any type, however.
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# Look up values with []
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@ -457,8 +457,7 @@ for i in range(4, 8, 2):
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print(i)
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"""
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To loop over a list, and retrieve both the index and the value of each item in the list
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prints:
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Loop over a list to retrieve both the index and the value of each list item:
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0 dog
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1 cat
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2 mouse
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@ -485,10 +484,11 @@ try:
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# Use "raise" to raise an error
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raise IndexError("This is an index error")
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except IndexError as e:
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pass # Pass is just a no-op. Usually you would do recovery here.
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pass # Refrain from this, provide a recovery (next example).
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except (TypeError, NameError):
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pass # Multiple exceptions can be handled together, if required.
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else: # Optional clause to the try/except block. Must follow all except blocks
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pass # Multiple exceptions can be processed jointly.
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else: # Optional clause to the try/except block. Must follow
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# all except blocks.
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print("All good!") # Runs only if the code in try raises no exceptions
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finally: # Execute under all circumstances
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print("We can clean up resources here")
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@ -524,7 +524,8 @@ print(contents)
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filled_dict = {"one": 1, "two": 2, "three": 3}
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our_iterable = filled_dict.keys()
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print(our_iterable) # => dict_keys(['one', 'two', 'three']). This is an object that implements our Iterable interface.
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print(our_iterable) # => dict_keys(['one', 'two', 'three']). This is an object
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# that implements our Iterable interface.
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# We can loop over it.
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for i in our_iterable:
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@ -544,7 +545,8 @@ next(our_iterator) # => "one"
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next(our_iterator) # => "two"
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next(our_iterator) # => "three"
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# After the iterator has returned all of its data, it raises a StopIteration exception
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# After the iterator has returned all of its data, it raises a
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# StopIteration exception
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next(our_iterator) # Raises StopIteration
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# We can also loop over it, in fact, "for" does this implicitly!
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@ -552,7 +554,7 @@ our_iterator = iter(our_iterable)
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for i in our_iterator:
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print(i) # Prints one, two, three
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# You can grab all the elements of an iterable or iterator by calling list() on it.
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# You can grab all the elements of an iterable or iterator by call of list().
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list(our_iterable) # => Returns ["one", "two", "three"]
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list(our_iterator) # => Returns [] because state is saved
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@ -602,9 +604,9 @@ all_the_args(1, 2, a=3, b=4) prints:
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# Use * to expand tuples and use ** to expand kwargs.
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args = (1, 2, 3, 4)
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kwargs = {"a": 3, "b": 4}
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all_the_args(*args) # equivalent to all_the_args(1, 2, 3, 4)
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all_the_args(**kwargs) # equivalent to all_the_args(a=3, b=4)
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all_the_args(*args, **kwargs) # equivalent to all_the_args(1, 2, 3, 4, a=3, b=4)
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all_the_args(*args) # equivalent: all_the_args(1, 2, 3, 4)
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all_the_args(**kwargs) # equivalent: all_the_args(a=3, b=4)
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all_the_args(*args, **kwargs) # equivalent: all_the_args(1, 2, 3, 4, a=3, b=4)
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# Returning multiple values (with tuple assignments)
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def swap(x, y):
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@ -614,7 +616,7 @@ def swap(x, y):
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x = 1
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y = 2
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x, y = swap(x, y) # => x = 2, y = 1
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# (x, y) = swap(x,y) # Again parenthesis have been excluded but can be included.
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# (x, y) = swap(x,y) # Again the use of parenthesis is optional.
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# global scope
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x = 5
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@ -662,7 +664,7 @@ list(map(max, [1, 2, 3], [4, 2, 1])) # => [4, 2, 3]
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list(filter(lambda x: x > 5, [3, 4, 5, 6, 7])) # => [6, 7]
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# We can use list comprehensions for nice maps and filters
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# List comprehension stores the output as a list which can itself be a nested list
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# List comprehension stores the output as a list (which itself may be nested).
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[add_10(i) for i in [1, 2, 3]] # => [11, 12, 13]
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[x for x in [3, 4, 5, 6, 7] if x > 5] # => [6, 7]
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@ -777,7 +779,7 @@ if __name__ == '__main__':
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i.say("hi") # "Ian: hi"
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j = Human("Joel")
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j.say("hello") # "Joel: hello"
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# i and j are instances of type Human, or in other words: they are Human objects
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# i and j are instances of type Human; i.e., they are Human objects.
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# Call our class method
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i.say(i.get_species()) # "Ian: H. sapiens"
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@ -939,8 +941,8 @@ class Batman(Superhero, Bat):
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# However we are dealing with multiple inheritance here, and super()
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# only works with the next base class in the MRO list.
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# So instead we explicitly call __init__ for all ancestors.
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# The use of *args and **kwargs allows for a clean way to pass arguments,
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# with each parent "peeling a layer of the onion".
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# The use of *args and **kwargs allows for a clean way to pass
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# arguments, with each parent "peeling a layer of the onion".
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Superhero.__init__(self, 'anonymous', movie=True,
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superpowers=['Wealthy'], *args, **kwargs)
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Bat.__init__(self, *args, can_fly=False, **kwargs)
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@ -1039,8 +1041,6 @@ print(say()) # Can you buy me a beer?
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print(say(say_please=True)) # Can you buy me a beer? Please! I am poor :(
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```
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## Ready For More?
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### Free Online
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* [Automate the Boring Stuff with Python](https://automatetheboringstuff.com)
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