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authorNed Batchelder <ned@nedbatchelder.com>2017-05-18 06:40:25 -0400
committerven <vendethiel@hotmail.fr>2017-05-18 12:40:25 +0200
commit9ccd1ee05ade8f2b76d8c473f34695b775330d31 (patch)
tree7a16019f4eab23496bc30b2f508e654e79958b23
parent6e3d29f036f9ede844f17e36e764b685d046adf9 (diff)
Some improvements to Python 3 (#2713)
-rw-r--r--python3.html.markdown49
1 files changed, 24 insertions, 25 deletions
diff --git a/python3.html.markdown b/python3.html.markdown
index cb53eaf8..f25d9228 100644
--- a/python3.html.markdown
+++ b/python3.html.markdown
@@ -9,7 +9,7 @@ contributors:
filename: learnpython3.py
---
-Python was created by Guido Van Rossum in the early 90s. It is now one of the most popular
+Python was created by Guido van Rossum in the early 90s. It is now one of the most popular
languages in existence. I fell in love with Python for its syntactic clarity. It's basically
executable pseudocode.
@@ -23,7 +23,7 @@ Note: This article applies to Python 3 specifically. Check out [here](http://lea
""" Multiline strings can be written
using three "s, and are often used
- as comments
+ as documentation.
"""
####################################################
@@ -114,7 +114,7 @@ b == a # => True, a's and b's objects are equal
# Strings can be added too! But try not to do this.
"Hello " + "world!" # => "Hello world!"
-# Strings can be added without using '+'
+# String literals (but not variables) can be concatenated without using '+'
"Hello " "world!" # => "Hello world!"
# A string can be treated like a list of characters
@@ -162,14 +162,14 @@ bool(()) # => False
print("I'm Python. Nice to meet you!") # => I'm Python. Nice to meet you!
# By default the print function also prints out a newline at the end.
-# Use the optional argument end to change the end character.
+# Use the optional argument end to change the end string.
print("Hello, World", end="!") # => Hello, World!
# Simple way to get input data from console
input_string_var = input("Enter some data: ") # Returns the data as a string
# Note: In earlier versions of Python, input() method was named as raw_input()
-# No need to declare variables before assigning to them.
+# There are no declarations, only assignments.
# Convention is to use lower_case_with_underscores
some_var = 5
some_var # => 5
@@ -206,6 +206,7 @@ li[-1] # => 3
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 end
@@ -277,7 +278,7 @@ d, e, f = 4, 5, 6
e, d = d, e # d is now 5 and e is now 4
-# Dictionaries store mappings
+# Dictionaries store mappings from keys to values
empty_dict = {}
# Here is a prefilled dictionary
filled_dict = {"one": 1, "two": 2, "three": 3}
@@ -323,7 +324,7 @@ filled_dict.setdefault("five", 6) # filled_dict["five"] is still 5
# Adding to a dictionary
filled_dict.update({"four":4}) # => {"one": 1, "two": 2, "three": 3, "four": 4}
-#filled_dict["four"] = 4 #another way to add to dict
+filled_dict["four"] = 4 # another way to add to dict
# Remove keys from a dictionary with del
del filled_dict["one"] # Removes the key "one" from filled dict
@@ -343,9 +344,6 @@ some_set = {1, 1, 2, 2, 3, 4} # some_set is now {1, 2, 3, 4}
invalid_set = {[1], 1} # => Raises a TypeError: unhashable type: 'list'
valid_set = {(1,), 1}
-# Can set new variables to a set
-filled_set = some_set
-
# Add one more item to the set
filled_set.add(5) # filled_set is now {1, 2, 3, 4, 5}
@@ -381,8 +379,9 @@ filled_set | other_set # => {1, 2, 3, 4, 5, 6}
# Let's just make a variable
some_var = 5
-# Here is an if statement. Indentation is significant in python!
-# prints "some_var is smaller than 10"
+# Here is an if statement. Indentation is significant in Python!
+# Convention is to use four spaces, not tabs.
+# This prints "some_var is smaller than 10"
if some_var > 10:
print("some_var is totally bigger than 10.")
elif some_var < 10: # This elif clause is optional.
@@ -470,7 +469,7 @@ with open("myfile.txt") as f:
# Python offers a fundamental abstraction called the Iterable.
# An iterable is an object that can be treated as a sequence.
-# The object returned the range function, is an iterable.
+# The object returned by the range function, is an iterable.
filled_dict = {"one": 1, "two": 2, "three": 3}
our_iterable = filled_dict.keys()
@@ -494,7 +493,7 @@ next(our_iterator) # => "one"
next(our_iterator) # => "two"
next(our_iterator) # => "three"
-# After the iterator has returned all of its data, it gives you a StopIteration Exception
+# 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.
@@ -566,13 +565,13 @@ x = 5
def set_x(num):
# Local var x not the same as global variable x
x = num # => 43
- print (x) # => 43
+ print(x) # => 43
def set_global_x(num):
global x
- print (x) # => 5
+ print(x) # => 5
x = num # global var x is now set to 6
- print (x) # => 6
+ print(x) # => 6
set_x(43)
set_global_x(6)
@@ -628,12 +627,12 @@ from math import *
import math as m
math.sqrt(16) == m.sqrt(16) # => True
-# Python modules are just ordinary python files. You
+# Python modules are just ordinary Python files. You
# can write your own, and import them. The name of the
# module is the same as the name of the file.
# You can find out which functions and attributes
-# defines a module.
+# are defined in a module.
import math
dir(math)
@@ -648,7 +647,7 @@ dir(math)
## 6. Classes
####################################################
-# We use the "class" operator to get a class
+# We use the "class" statement to create a class
class Human:
# A class attribute. It is shared by all instances of this class
@@ -656,9 +655,9 @@ class Human:
# Basic initializer, this is called when this class is instantiated.
# Note that the double leading and trailing underscores denote objects
- # or attributes that are used by python but that live in user-controlled
+ # or attributes that are used by Python but that live in user-controlled
# namespaces. Methods(or objects or attributes) like: __init__, __str__,
- # __repr__ etc. are called magic methods (or sometimes called dunder methods)
+ # __repr__ etc. are called special methods (or sometimes called dunder methods)
# You should not invent such names on your own.
def __init__(self, name):
# Assign the argument to the instance's name attribute
@@ -687,8 +686,8 @@ class Human:
return "*grunt*"
# A property is just like a getter.
- # It turns the method age() into an read-only attribute
- # of the same name.
+ # It turns the method age() into an read-only attribute of the same name.
+ # There's no need to write trivial getters and setters in Python, though.
@property
def age(self):
return self._age
@@ -768,7 +767,7 @@ if __name__ == '__main__':
# To take advantage of modularization by file you could place the classes above in their own files,
# say, human.py and bat.py
-# to import functions from other files use the following format
+# To import functions from other files use the following format
# from "filename-without-extension" import "function-or-class"
# superhero.py