diff options
Diffstat (limited to 'python3.html.markdown')
| -rw-r--r-- | python3.html.markdown | 63 |
1 files changed, 49 insertions, 14 deletions
diff --git a/python3.html.markdown b/python3.html.markdown index c4f15867..20377801 100644 --- a/python3.html.markdown +++ b/python3.html.markdown @@ -8,6 +8,7 @@ contributors: - ["evuez", "http://github.com/evuez"] - ["Rommel Martinez", "https://ebzzry.io"] - ["Roberto Fernandez Diaz", "https://github.com/robertofd1995"] + - ["caminsha", "https://github.com/caminsha"] filename: learnpython3.py --- @@ -57,11 +58,12 @@ Note: This article applies to Python 3 specifically. Check out [here](http://lea 2**3 # => 8 # Enforce precedence with parentheses +1 + 3 * 2 # => 7 (1 + 3) * 2 # => 8 # Boolean values are primitives (Note: the capitalization) -True -False +True # => True +False # => False # negate with not not True # => False @@ -155,7 +157,7 @@ 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 @@ -228,15 +230,11 @@ li[4] # Raises an IndexError # You can look at ranges with slice syntax. # The start index is included, the end index is not # (It's a closed/open range for you mathy types.) -li[1:3] # => [2, 4] -# Omit the beginning and return the list -li[2:] # => [4, 3] -# Omit the end and return the list -li[:3] # => [1, 2, 4] -# Select every second entry -li[::2] # =>[1, 4] -# Return a reversed copy of the list -li[::-1] # => [3, 4, 2, 1] +li[1:3] # Return list from index 1 to 3 => [2, 4] +li[2:] # Return list starting from index 2 => [4, 3] +li[:3] # Return list from beginning until index 3 => [1, 2, 4] +li[::2] # Return list selecting every second entry => [1, 4] +li[::-1] # Return list in reverse order => [3, 4, 2, 1] # Use any combination of these to make advanced slices # li[start:end:step] @@ -462,8 +460,19 @@ 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 """ +animals = ["dog", "cat", "mouse"] +for i, value in enumerate(animals): + print(i, value) +""" While loops go until a condition is no longer met. prints: 0 @@ -494,6 +503,26 @@ with open("myfile.txt") as f: for line in f: print(line) +# Writing to a file +contents = {"aa": 12, "bb": 21} +with open("myfile1.txt", "w+") as file: + file.write(str(contents)) # writes a string to a file + +with open("myfile2.txt", "w+") as file: + file.write(json.dumps(contents)) # writes an object to a file + +# Reading from a file +with open('myfile1.txt', "r+") as file: + contents = file.read() # reads a string from a file +print(contents) +# print: {"aa": 12, "bb": 21} + +with open('myfile2.txt', "r+") as file: + contents = json.load(file) # reads a json object from a file +print(contents) +# print: {"aa": 12, "bb": 21} + + # Python offers a fundamental abstraction called the Iterable. # An iterable is an object that can be treated as a sequence. # The object returned by the range function, is an iterable. @@ -523,8 +552,14 @@ next(our_iterator) # => "three" # After the iterator has returned all of its data, it raises a StopIteration exception next(our_iterator) # Raises StopIteration -# You can grab all the elements of an iterator by calling list() on it. -list(filled_dict.keys()) # => Returns ["one", "two", "three"] +# We can also loop over it, in fact, "for" does this implicitly! +our_iterator = iter(our_iterable) +for i in our_iterator: + print(i) # Prints one, two, three + +# You can grab all the elements of an iterable or iterator by calling list() on it. +list(our_iterable) # => Returns ["one", "two", "three"] +list(our_iterator) # => Returns [] because state is saved #################################################### |