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mirror of https://github.com/adambard/learnxinyminutes-docs.git synced 2025-08-11 09:14:39 +02:00

Made the file pep8 compliant (#2601)

Actually nearly compliant, I ran `pep8 code.py --ignore=E402,E501,E712`
This commit is contained in:
David Haberthür
2016-12-20 15:04:12 +01:00
committed by ven
parent 919e44f843
commit 4737819e5d

View File

@@ -5,6 +5,7 @@ contributors:
- ["Amin Bandali", "http://aminbandali.com"] - ["Amin Bandali", "http://aminbandali.com"]
- ["Andre Polykanine", "https://github.com/Oire"] - ["Andre Polykanine", "https://github.com/Oire"]
- ["evuez", "http://github.com/evuez"] - ["evuez", "http://github.com/evuez"]
- ["habi", "http://github.com/habi"]
filename: learnpython.py filename: learnpython.py
--- ---
@@ -34,9 +35,8 @@ Python 3 tutorial.
as comments as comments
""" """
#################################################### ####################################################
## 1. Primitive Datatypes and Operators # 1. Primitive Datatypes and Operators
#################################################### ####################################################
# You have numbers # You have numbers
@@ -53,41 +53,42 @@ Python 3 tutorial.
5 / 2 # => 2 5 / 2 # => 2
# To fix division we need to learn about floats. # To fix division we need to learn about floats.
2.0 # This is a float 2.0 # This is a float
11.0 / 4.0 # => 2.75 ahhh...much better 11.0 / 4.0 # => 2.75 ahhh...much better
# Result of integer division truncated down both for positive and negative. # Result of integer division truncated down both for positive and negative.
5 // 3 # => 1 5 // 3 # => 1
5.0 // 3.0 # => 1.0 # works on floats too 5.0 // 3.0 # => 1.0 # works on floats too
-5 // 3 # => -2 -5 // 3 # => -2
-5.0 // 3.0 # => -2.0 -5.0 // 3.0 # => -2.0
# Note that we can also import division module(Section 6 Modules) # Note that we can also import division module(Section 6 Modules)
# to carry out normal division with just one '/'. # to carry out normal division with just one '/'.
from __future__ import division from __future__ import division
11/4 # => 2.75 ...normal division
11//4 # => 2 ...floored division 11 / 4 # => 2.75 ...normal division
11 // 4 # => 2 ...floored division
# Modulo operation # Modulo operation
7 % 3 # => 1 7 % 3 # => 1
# Exponentiation (x to the yth power) # Exponentiation (x to the yth power)
2**4 # => 16 2 ** 4 # => 16
# Enforce precedence with parentheses # Enforce precedence with parentheses
(1 + 3) * 2 # => 8 (1 + 3) * 2 # => 8
# Boolean Operators # Boolean Operators
# Note "and" and "or" are case-sensitive # Note "and" and "or" are case-sensitive
True and False #=> False True and False # => False
False or True #=> True False or True # => True
# Note using Bool operators with ints # Note using Bool operators with ints
0 and 2 #=> 0 0 and 2 # => 0
-5 or 0 #=> -5 -5 or 0 # => -5
0 == False #=> True 0 == False # => True
2 == True #=> False 2 == True # => False
1 == True #=> True 1 == True # => True
# negate with not # negate with not
not True # => False not True # => False
@@ -129,12 +130,12 @@ not False # => True
# You can find the length of a string # You can find the length of a string
len("This is a string") # => 16 len("This is a string") # => 16
#String formatting with % # String formatting with %
#Even though the % string operator will be deprecated on Python 3.1 and removed # Even though the % string operator will be deprecated on Python 3.1 and removed
#later at some time, it may still be good to know how it works. # later at some time, it may still be good to know how it works.
x = 'apple' x = 'apple'
y = 'lemon' y = 'lemon'
z = "The items in the basket are %s and %s" % (x,y) z = "The items in the basket are %s and %s" % (x, y)
# A newer way to format strings is the format method. # A newer way to format strings is the format method.
# This method is the preferred way # This method is the preferred way
@@ -170,20 +171,21 @@ bool("") # => False
#################################################### ####################################################
## 2. Variables and Collections # 2. Variables and Collections
#################################################### ####################################################
# Python has a print statement # Python has a print statement
print "I'm Python. Nice to meet you!" # => I'm Python. Nice to meet you! print "I'm Python. Nice to meet you!" # => I'm Python. Nice to meet you!
# Simple way to get input data from console # Simple way to get input data from console
input_string_var = raw_input("Enter some data: ") # Returns the data as a string input_string_var = raw_input(
input_var = input("Enter some data: ") # Evaluates the data as python code "Enter some data: ") # Returns the data as a string
input_var = input("Enter some data: ") # Evaluates the data as python code
# Warning: Caution is recommended for input() method usage # Warning: Caution is recommended for input() method usage
# Note: In python 3, input() is deprecated and raw_input() is renamed to input() # Note: In python 3, input() is deprecated and raw_input() is renamed to input()
# No need to declare variables before assigning to them. # No need to declare variables before assigning to them.
some_var = 5 # Convention is to use lower_case_with_underscores some_var = 5 # Convention is to use lower_case_with_underscores
some_var # => 5 some_var # => 5
# Accessing a previously unassigned variable is an exception. # Accessing a previously unassigned variable is an exception.
@@ -194,21 +196,20 @@ some_other_var # Raises a name error
# Equivalent of C's '?:' ternary operator # Equivalent of C's '?:' ternary operator
"yahoo!" if 3 > 2 else 2 # => "yahoo!" "yahoo!" if 3 > 2 else 2 # => "yahoo!"
# Lists store sequences # Lists store sequences
li = [] li = []
# You can start with a prefilled list # You can start with a prefilled list
other_li = [4, 5, 6] other_li = [4, 5, 6]
# Add stuff to the end of a list with append # Add stuff to the end of a list with append
li.append(1) # li is now [1] li.append(1) # li is now [1]
li.append(2) # li is now [1, 2] li.append(2) # li is now [1, 2]
li.append(4) # li is now [1, 2, 4] li.append(4) # li is now [1, 2, 4]
li.append(3) # li is now [1, 2, 4, 3] li.append(3) # li is now [1, 2, 4, 3]
# Remove from the end with pop # Remove from the end with pop
li.pop() # => 3 and li is now [1, 2, 4] li.pop() # => 3 and li is now [1, 2, 4]
# Let's put it back # Let's put it back
li.append(3) # li is now [1, 2, 4, 3] again. li.append(3) # li is now [1, 2, 4, 3] again.
# Access a list like you would any array # Access a list like you would any array
li[0] # => 1 li[0] # => 1
@@ -230,21 +231,21 @@ li[2:] # => [4, 3]
# Omit the end # Omit the end
li[:3] # => [1, 2, 4] li[:3] # => [1, 2, 4]
# Select every second entry # Select every second entry
li[::2] # =>[1, 4] li[::2] # =>[1, 4]
# Reverse a copy of the list # Reverse a copy of the list
li[::-1] # => [3, 4, 2, 1] li[::-1] # => [3, 4, 2, 1]
# Use any combination of these to make advanced slices # Use any combination of these to make advanced slices
# li[start:end:step] # li[start:end:step]
# Remove arbitrary elements from a list with "del" # Remove arbitrary elements from a list with "del"
del li[2] # li is now [1, 2, 3] del li[2] # li is now [1, 2, 3]
# You can add lists # You can add lists
li + other_li # => [1, 2, 3, 4, 5, 6] li + other_li # => [1, 2, 3, 4, 5, 6]
# Note: values for li and for other_li are not modified. # Note: values for li and for other_li are not modified.
# Concatenate lists with "extend()" # Concatenate lists with "extend()"
li.extend(other_li) # Now li is [1, 2, 3, 4, 5, 6] li.extend(other_li) # Now li is [1, 2, 3, 4, 5, 6]
# Remove first occurrence of a value # Remove first occurrence of a value
li.remove(2) # li is now [1, 3, 4, 5, 6] li.remove(2) # li is now [1, 3, 4, 5, 6]
@@ -258,31 +259,29 @@ li.index(2) # => 1
li.index(7) # Raises a ValueError as 7 is not in the list li.index(7) # Raises a ValueError as 7 is not in the list
# Check for existence in a list with "in" # Check for existence in a list with "in"
1 in li # => True 1 in li # => True
# Examine the length with "len()" # Examine the length with "len()"
len(li) # => 6 len(li) # => 6
# Tuples are like lists but are immutable. # Tuples are like lists but are immutable.
tup = (1, 2, 3) tup = (1, 2, 3)
tup[0] # => 1 tup[0] # => 1
tup[0] = 3 # Raises a TypeError tup[0] = 3 # Raises a TypeError
# You can do all those list thingies on tuples too # You can do all those list thingies on tuples too
len(tup) # => 3 len(tup) # => 3
tup + (4, 5, 6) # => (1, 2, 3, 4, 5, 6) tup + (4, 5, 6) # => (1, 2, 3, 4, 5, 6)
tup[:2] # => (1, 2) tup[:2] # => (1, 2)
2 in tup # => True 2 in tup # => True
# You can unpack tuples (or lists) into variables # You can unpack tuples (or lists) into variables
a, b, c = (1, 2, 3) # a is now 1, b is now 2 and c is now 3 a, b, c = (1, 2, 3) # a is now 1, b is now 2 and c is now 3
d, e, f = 4, 5, 6 # you can leave out the parentheses d, e, f = 4, 5, 6 # you can leave out the parentheses
# Tuples are created by default if you leave out the parentheses # Tuples are created by default if you leave out the parentheses
g = 4, 5, 6 # => (4, 5, 6) g = 4, 5, 6 # => (4, 5, 6)
# Now look how easy it is to swap two values # Now look how easy it is to swap two values
e, d = d, e # d is now 5 and e is now 4 e, d = d, e # d is now 5 and e is now 4
# Dictionaries store mappings # Dictionaries store mappings
empty_dict = {} empty_dict = {}
@@ -290,33 +289,33 @@ empty_dict = {}
filled_dict = {"one": 1, "two": 2, "three": 3} filled_dict = {"one": 1, "two": 2, "three": 3}
# Look up values with [] # Look up values with []
filled_dict["one"] # => 1 filled_dict["one"] # => 1
# Get all keys as a list with "keys()" # Get all keys as a list with "keys()"
filled_dict.keys() # => ["three", "two", "one"] filled_dict.keys() # => ["three", "two", "one"]
# Note - Dictionary key ordering is not guaranteed. # Note - Dictionary key ordering is not guaranteed.
# Your results might not match this exactly. # Your results might not match this exactly.
# Get all values as a list with "values()" # Get all values as a list with "values()"
filled_dict.values() # => [3, 2, 1] filled_dict.values() # => [3, 2, 1]
# Note - Same as above regarding key ordering. # Note - Same as above regarding key ordering.
# Get all key-value pairs as a list of tuples with "items()" # Get all key-value pairs as a list of tuples with "items()"
filled_dicts.items() # => [("one", 1), ("two", 2), ("three", 3)] filled_dicts.items() # => [("one", 1), ("two", 2), ("three", 3)]
# Check for existence of keys in a dictionary with "in" # Check for existence of keys in a dictionary with "in"
"one" in filled_dict # => True "one" in filled_dict # => True
1 in filled_dict # => False 1 in filled_dict # => False
# Looking up a non-existing key is a KeyError # Looking up a non-existing key is a KeyError
filled_dict["four"] # KeyError filled_dict["four"] # KeyError
# Use "get()" method to avoid the KeyError # Use "get()" method to avoid the KeyError
filled_dict.get("one") # => 1 filled_dict.get("one") # => 1
filled_dict.get("four") # => None filled_dict.get("four") # => None
# The get method supports a default argument when the value is missing # The get method supports a default argument when the value is missing
filled_dict.get("one", 4) # => 1 filled_dict.get("one", 4) # => 1
filled_dict.get("four", 4) # => 4 filled_dict.get("four", 4) # => 4
# note that filled_dict.get("four") is still => None # note that filled_dict.get("four") is still => None
# (get doesn't set the value in the dictionary) # (get doesn't set the value in the dictionary)
@@ -327,47 +326,46 @@ filled_dict["four"] = 4 # now, filled_dict["four"] => 4
filled_dict.setdefault("five", 5) # filled_dict["five"] is set to 5 filled_dict.setdefault("five", 5) # filled_dict["five"] is set to 5
filled_dict.setdefault("five", 6) # filled_dict["five"] is still 5 filled_dict.setdefault("five", 6) # filled_dict["five"] is still 5
# Sets store ... well sets (which are like lists but can contain no duplicates) # Sets store ... well sets (which are like lists but can contain no duplicates)
empty_set = set() empty_set = set()
# Initialize a "set()" with a bunch of values # Initialize a "set()" with a bunch of values
some_set = set([1, 2, 2, 3, 4]) # some_set is now set([1, 2, 3, 4]) some_set = set([1, 2, 2, 3, 4]) # some_set is now set([1, 2, 3, 4])
# order is not guaranteed, even though it may sometimes look sorted # order is not guaranteed, even though it may sometimes look sorted
another_set = set([4, 3, 2, 2, 1]) # another_set is now set([1, 2, 3, 4]) another_set = set([4, 3, 2, 2, 1]) # another_set is now set([1, 2, 3, 4])
# Since Python 2.7, {} can be used to declare a set # Since Python 2.7, {} can be used to declare a set
filled_set = {1, 2, 2, 3, 4} # => {1, 2, 3, 4} filled_set = {1, 2, 2, 3, 4} # => {1, 2, 3, 4}
# Add more items to a set # Add more items to a set
filled_set.add(5) # filled_set is now {1, 2, 3, 4, 5} filled_set.add(5) # filled_set is now {1, 2, 3, 4, 5}
# Do set intersection with & # Do set intersection with &
other_set = {3, 4, 5, 6} other_set = {3, 4, 5, 6}
filled_set & other_set # => {3, 4, 5} filled_set & other_set # => {3, 4, 5}
# Do set union with | # Do set union with |
filled_set | other_set # => {1, 2, 3, 4, 5, 6} filled_set | other_set # => {1, 2, 3, 4, 5, 6}
# Do set difference with - # Do set difference with -
{1, 2, 3, 4} - {2, 3, 5} # => {1, 4} {1, 2, 3, 4} - {2, 3, 5} # => {1, 4}
# Do set symmetric difference with ^ # Do set symmetric difference with ^
{1, 2, 3, 4} ^ {2, 3, 5} # => {1, 4, 5} {1, 2, 3, 4} ^ {2, 3, 5} # => {1, 4, 5}
# Check if set on the left is a superset of set on the right # Check if set on the left is a superset of set on the right
{1, 2} >= {1, 2, 3} # => False {1, 2} >= {1, 2, 3} # => False
# Check if set on the left is a subset of set on the right # Check if set on the left is a subset of set on the right
{1, 2} <= {1, 2, 3} # => True {1, 2} <= {1, 2, 3} # => True
# Check for existence in a set with in # Check for existence in a set with in
2 in filled_set # => True 2 in filled_set # => True
10 in filled_set # => False 10 in filled_set # => False
#################################################### ####################################################
## 3. Control Flow # 3. Control Flow
#################################################### ####################################################
# Let's just make a variable # Let's just make a variable
@@ -377,12 +375,11 @@ some_var = 5
# prints "some_var is smaller than 10" # prints "some_var is smaller than 10"
if some_var > 10: if some_var > 10:
print "some_var is totally bigger than 10." print "some_var is totally bigger than 10."
elif some_var < 10: # This elif clause is optional. elif some_var < 10: # This elif clause is optional.
print "some_var is smaller than 10." print "some_var is smaller than 10."
else: # This is optional too. else: # This is optional too.
print "some_var is indeed 10." print "some_var is indeed 10."
""" """
For loops iterate over lists For loops iterate over lists
prints: prints:
@@ -438,12 +435,12 @@ try:
# Use "raise" to raise an error # Use "raise" to raise an error
raise IndexError("This is an index error") raise IndexError("This is an index error")
except IndexError as e: except IndexError as e:
pass # Pass is just a no-op. Usually you would do recovery here. pass # Pass is just a no-op. Usually you would do recovery here.
except (TypeError, NameError): except (TypeError, NameError):
pass # Multiple exceptions can be handled together, if required. pass # Multiple exceptions can be handled together, if required.
else: # Optional clause to the try/except block. Must follow all except blocks else: # Optional clause to the try/except block. Must follow all except blocks
print "All good!" # Runs only if the code in try raises no exceptions print "All good!" # Runs only if the code in try raises no exceptions
finally: # Execute under all circumstances finally: # Execute under all circumstances
print "We can clean up resources here" print "We can clean up resources here"
# Instead of try/finally to cleanup resources you can use a with statement # Instead of try/finally to cleanup resources you can use a with statement
@@ -453,19 +450,20 @@ with open("myfile.txt") as f:
#################################################### ####################################################
## 4. Functions # 4. Functions
#################################################### ####################################################
# Use "def" to create new functions # Use "def" to create new functions
def add(x, y): def add(x, y):
print "x is {0} and y is {1}".format(x, y) print "x is {0} and y is {1}".format(x, y)
return x + y # Return values with a return statement return x + y # Return values with a return statement
# Calling functions with parameters # Calling functions with parameters
add(5, 6) # => prints out "x is 5 and y is 6" and returns 11 add(5, 6) # => prints out "x is 5 and y is 6" and returns 11
# Another way to call functions is with keyword arguments # Another way to call functions is with keyword arguments
add(y=6, x=5) # Keyword arguments can arrive in any order. add(y=6, x=5) # Keyword arguments can arrive in any order.
# You can define functions that take a variable number of # You can define functions that take a variable number of
@@ -473,21 +471,26 @@ add(y=6, x=5) # Keyword arguments can arrive in any order.
def varargs(*args): def varargs(*args):
return args return args
varargs(1, 2, 3) # => (1, 2, 3)
varargs(1, 2, 3) # => (1, 2, 3)
# You can define functions that take a variable number of # You can define functions that take a variable number of
# keyword args, as well, which will be interpreted as a dict by using ** # keyword args, as well, which will be interpreted as a dict by using **
def keyword_args(**kwargs): def keyword_args(**kwargs):
return kwargs return kwargs
# Let's call it to see what happens # Let's call it to see what happens
keyword_args(big="foot", loch="ness") # => {"big": "foot", "loch": "ness"} keyword_args(big="foot", loch="ness") # => {"big": "foot", "loch": "ness"}
# You can do both at once, if you like # You can do both at once, if you like
def all_the_args(*args, **kwargs): def all_the_args(*args, **kwargs):
print args print args
print kwargs print kwargs
""" """
all_the_args(1, 2, a=3, b=4) prints: all_the_args(1, 2, a=3, b=4) prints:
(1, 2) (1, 2)
@@ -498,9 +501,10 @@ all_the_args(1, 2, a=3, b=4) prints:
# Use * to expand positional args and use ** to expand keyword args. # Use * to expand positional args and use ** to expand keyword args.
args = (1, 2, 3, 4) args = (1, 2, 3, 4)
kwargs = {"a": 3, "b": 4} kwargs = {"a": 3, "b": 4}
all_the_args(*args) # equivalent to foo(1, 2, 3, 4) all_the_args(*args) # equivalent to foo(1, 2, 3, 4)
all_the_args(**kwargs) # equivalent to foo(a=3, b=4) all_the_args(**kwargs) # equivalent to foo(a=3, b=4)
all_the_args(*args, **kwargs) # equivalent to foo(1, 2, 3, 4, a=3, b=4) all_the_args(*args, **kwargs) # equivalent to foo(1, 2, 3, 4, a=3, b=4)
# you can pass args and kwargs along to other functions that take args/kwargs # you can pass args and kwargs along to other functions that take args/kwargs
# by expanding them with * and ** respectively # by expanding them with * and ** respectively
@@ -509,58 +513,64 @@ def pass_all_the_args(*args, **kwargs):
print varargs(*args) print varargs(*args)
print keyword_args(**kwargs) print keyword_args(**kwargs)
# Function Scope # Function Scope
x = 5 x = 5
def set_x(num): def set_x(num):
# Local var x not the same as global variable x # Local var x not the same as global variable x
x = num # => 43 x = num # => 43
print x # => 43 print x # => 43
def set_global_x(num): def set_global_x(num):
global x global x
print x # => 5 print x # => 5
x = num # global var x is now set to 6 x = num # global var x is now set to 6
print x # => 6 print x # => 6
set_x(43) set_x(43)
set_global_x(6) set_global_x(6)
# Python has first class functions # Python has first class functions
def create_adder(x): def create_adder(x):
def adder(y): def adder(y):
return x + y return x + y
return adder return adder
add_10 = create_adder(10) add_10 = create_adder(10)
add_10(3) # => 13 add_10(3) # => 13
# There are also anonymous functions # There are also anonymous functions
(lambda x: x > 2)(3) # => True (lambda x: x > 2)(3) # => True
(lambda x, y: x ** 2 + y ** 2)(2, 1) # => 5 (lambda x, y: x ** 2 + y ** 2)(2, 1) # => 5
# There are built-in higher order functions # There are built-in higher order functions
map(add_10, [1, 2, 3]) # => [11, 12, 13] map(add_10, [1, 2, 3]) # => [11, 12, 13]
map(max, [1, 2, 3], [4, 2, 1]) # => [4, 2, 3] map(max, [1, 2, 3], [4, 2, 1]) # => [4, 2, 3]
filter(lambda x: x > 5, [3, 4, 5, 6, 7]) # => [6, 7] filter(lambda x: x > 5, [3, 4, 5, 6, 7]) # => [6, 7]
# We can use list comprehensions for nice maps and filters # We can use list comprehensions for nice maps and filters
[add_10(i) for i in [1, 2, 3]] # => [11, 12, 13] [add_10(i) for i in [1, 2, 3]] # => [11, 12, 13]
[x for x in [3, 4, 5, 6, 7] if x > 5] # => [6, 7] [x for x in [3, 4, 5, 6, 7] if x > 5] # => [6, 7]
# You can construct set and dict comprehensions as well. # You can construct set and dict comprehensions as well.
{x for x in 'abcddeef' if x in 'abc'} # => {'a', 'b', 'c'} {x for x in 'abcddeef' if x in 'abc'} # => {'a', 'b', 'c'}
{x: x**2 for x in range(5)} # => {0: 0, 1: 1, 2: 4, 3: 9, 4: 16} {x: x ** 2 for x in range(5)} # => {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}
#################################################### ####################################################
## 5. Classes # 5. Classes
#################################################### ####################################################
# We subclass from object to get a class. # We subclass from object to get a class.
class Human(object): class Human(object):
# A class attribute. It is shared by all instances of this class # A class attribute. It is shared by all instances of this class
species = "H. sapiens" species = "H. sapiens"
@@ -575,7 +585,6 @@ class Human(object):
# Initialize property # Initialize property
self.age = 0 self.age = 0
# An instance method. All methods take "self" as the first argument # An instance method. All methods take "self" as the first argument
def say(self, msg): def say(self, msg):
return "{0}: {1}".format(self.name, msg) return "{0}: {1}".format(self.name, msg)
@@ -611,45 +620,46 @@ class Human(object):
# Instantiate a class # Instantiate a class
i = Human(name="Ian") i = Human(name="Ian")
print i.say("hi") # prints out "Ian: hi" print i.say("hi") # prints out "Ian: hi"
j = Human("Joel") j = Human("Joel")
print j.say("hello") # prints out "Joel: hello" print j.say("hello") # prints out "Joel: hello"
# Call our class method # Call our class method
i.get_species() # => "H. sapiens" i.get_species() # => "H. sapiens"
# Change the shared attribute # Change the shared attribute
Human.species = "H. neanderthalensis" Human.species = "H. neanderthalensis"
i.get_species() # => "H. neanderthalensis" i.get_species() # => "H. neanderthalensis"
j.get_species() # => "H. neanderthalensis" j.get_species() # => "H. neanderthalensis"
# Call the static method # Call the static method
Human.grunt() # => "*grunt*" Human.grunt() # => "*grunt*"
# Update the property # Update the property
i.age = 42 i.age = 42
# Get the property # Get the property
i.age # => 42 i.age # => 42
# Delete the property # Delete the property
del i.age del i.age
i.age # => raises an AttributeError i.age # => raises an AttributeError
#################################################### ####################################################
## 6. Modules # 6. Modules
#################################################### ####################################################
# You can import modules # You can import modules
import math import math
print math.sqrt(16) # => 4 print math.sqrt(16) # => 4
# You can get specific functions from a module # You can get specific functions from a module
from math import ceil, floor from math import ceil, floor
print ceil(3.7) # => 4.0 print ceil(3.7) # => 4.0
print floor(3.7) # => 3.0 print floor(3.7) # => 3.0
# You can import all functions from a module. # You can import all functions from a module.
# Warning: this is not recommended # Warning: this is not recommended
@@ -657,9 +667,11 @@ from math import *
# You can shorten module names # You can shorten module names
import math as m import math as m
math.sqrt(16) == m.sqrt(16) # => True
math.sqrt(16) == m.sqrt(16) # => True
# you can also test that the functions are equivalent # you can also test that the functions are equivalent
from math import sqrt from math import sqrt
math.sqrt == m.sqrt == sqrt # => True math.sqrt == m.sqrt == sqrt # => True
# Python modules are just ordinary python files. You # Python modules are just ordinary python files. You
@@ -669,8 +681,10 @@ math.sqrt == m.sqrt == sqrt # => True
# You can find out which functions and attributes # You can find out which functions and attributes
# defines a module. # defines a module.
import math import math
dir(math) dir(math)
# If you have a Python script named math.py in the same # If you have a Python script named math.py in the same
# folder as your current script, the file math.py will # folder as your current script, the file math.py will
# be loaded instead of the built-in Python module. # be loaded instead of the built-in Python module.
@@ -679,7 +693,7 @@ dir(math)
#################################################### ####################################################
## 7. Advanced # 7. Advanced
#################################################### ####################################################
# Generators # Generators
@@ -693,6 +707,7 @@ def double_numbers(iterable):
for i in iterable: for i in iterable:
double_arr.append(i + i) double_arr.append(i + i)
# Running the following would mean we'll double all values first and return all # Running the following would mean we'll double all values first and return all
# of them back to be checked by our condition # of them back to be checked by our condition
for value in double_numbers(range(1000000)): # `test_non_generator` for value in double_numbers(range(1000000)): # `test_non_generator`
@@ -700,12 +715,14 @@ for value in double_numbers(range(1000000)): # `test_non_generator`
if value > 5: if value > 5:
break break
# We could instead use a generator to "generate" the doubled value as the item # We could instead use a generator to "generate" the doubled value as the item
# is being requested # is being requested
def double_numbers_generator(iterable): def double_numbers_generator(iterable):
for i in iterable: for i in iterable:
yield i + i yield i + i
# Running the same code as before, but with a generator, now allows us to iterate # Running the same code as before, but with a generator, now allows us to iterate
# over the values and doubling them one by one as they are being consumed by # over the values and doubling them one by one as they are being consumed by
# our logic. Hence as soon as we see a value > 5, we break out of the # our logic. Hence as soon as we see a value > 5, we break out of the
@@ -723,22 +740,22 @@ for value in double_numbers_generator(xrange(1000000)): # `test_generator`
# Just as you can create a list comprehension, you can create generator # Just as you can create a list comprehension, you can create generator
# comprehensions as well. # comprehensions as well.
values = (-x for x in [1,2,3,4,5]) values = (-x for x in [1, 2, 3, 4, 5])
for x in values: for x in values:
print(x) # prints -1 -2 -3 -4 -5 to console/terminal print(x) # prints -1 -2 -3 -4 -5 to console/terminal
# You can also cast a generator comprehension directly to a list. # You can also cast a generator comprehension directly to a list.
values = (-x for x in [1,2,3,4,5]) values = (-x for x in [1, 2, 3, 4, 5])
gen_to_list = list(values) gen_to_list = list(values)
print(gen_to_list) # => [-1, -2, -3, -4, -5] print(gen_to_list) # => [-1, -2, -3, -4, -5]
# Decorators # Decorators
# in this example beg wraps say # in this example beg wraps say
# Beg will call say. If say_please is True then it will change the returned # Beg will call say. If say_please is True then it will change the returned
# message # message
from functools import wraps from functools import wraps
def beg(target_function): def beg(target_function):
@wraps(target_function) @wraps(target_function)
def wrapper(*args, **kwargs): def wrapper(*args, **kwargs):
@@ -749,11 +766,13 @@ def beg(target_function):
return wrapper return wrapper
@beg @beg
def say(say_please=False): def say(say_please=False):
msg = "Can you buy me a beer?" msg = "Can you buy me a beer?"
return msg, say_please return msg, say_please
print say() # Can you buy me a beer? print say() # Can you buy me a beer?
print say(say_please=True) # Can you buy me a beer? Please! I am poor :( print say(say_please=True) # Can you buy me a beer? Please! I am poor :(
``` ```