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Range is not a generator
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@ -96,7 +96,7 @@ False or True #=> True
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1 < 2 < 3 # => True
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2 < 3 < 2 # => False
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# (is vs. ==) is checks if two variable refer to the same object, but == checks
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# (is vs. ==) is checks if two variable refer to the same object, but == checks
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# if the objects pointed to have the same values.
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a = [1, 2, 3, 4] # Point a at a new list, [1, 2, 3, 4]
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b = a # Point b at what a is pointing to
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@ -256,8 +256,8 @@ empty_dict = {}
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# Here is a prefilled dictionary
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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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# 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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valid_dict = {(1,2,3):[1,2,3]} # Values can be of any type, however.
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@ -423,7 +423,7 @@ else: # Optional clause to the try/except block. Must follow 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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# Instead of try/finally to cleanup resources you can use a with statement
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with open("myfile.txt") as f:
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for line in f:
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@ -661,8 +661,6 @@ def double_numbers(iterable):
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# Instead of generating and returning all values at once it creates one in each
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# iteration. This means values bigger than 15 wont be processed in
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# double_numbers.
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# Note range is a generator too. Creating a list 1-900000000 would take lot of
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# time to be made
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# We use a trailing underscore in variable names when we want to use a name that
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# would normally collide with a python keyword
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range_ = range(1, 900000000)
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