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authorDavid Haberthür <email@davidhaberthuer.ch>2016-12-20 15:04:12 +0100
committerven <vendethiel@hotmail.fr>2016-12-20 15:04:12 +0100
commit4737819e5da9e399b312b04417b1b2526f8907be (patch)
treef5555d5b7bc085e31e5ef60bfc3045912a0470db
parent919e44f843b4496448078cae8c1184da336c197f (diff)
Made the file `pep8` compliant (#2601)
Actually nearly compliant, I ran `pep8 code.py --ignore=E402,E501,E712`
-rw-r--r--python.html.markdown261
1 files changed, 140 insertions, 121 deletions
diff --git a/python.html.markdown b/python.html.markdown
index 050503c3..52ad6308 100644
--- a/python.html.markdown
+++ b/python.html.markdown
@@ -5,6 +5,7 @@ contributors:
- ["Amin Bandali", "http://aminbandali.com"]
- ["Andre Polykanine", "https://github.com/Oire"]
- ["evuez", "http://github.com/evuez"]
+ - ["habi", "http://github.com/habi"]
filename: learnpython.py
---
@@ -34,9 +35,8 @@ Python 3 tutorial.
as comments
"""
-
####################################################
-## 1. Primitive Datatypes and Operators
+# 1. Primitive Datatypes and Operators
####################################################
# You have numbers
@@ -53,41 +53,42 @@ Python 3 tutorial.
5 / 2 # => 2
# 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
# Result of integer division truncated down both for positive and negative.
-5 // 3 # => 1
-5.0 // 3.0 # => 1.0 # works on floats too
+5 // 3 # => 1
+5.0 // 3.0 # => 1.0 # works on floats too
-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)
# to carry out normal division with just one '/'.
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
-7 % 3 # => 1
+7 % 3 # => 1
# Exponentiation (x to the yth power)
-2**4 # => 16
+2 ** 4 # => 16
# Enforce precedence with parentheses
(1 + 3) * 2 # => 8
# Boolean Operators
# Note "and" and "or" are case-sensitive
-True and False #=> False
-False or True #=> True
+True and False # => False
+False or True # => True
# Note using Bool operators with ints
-0 and 2 #=> 0
--5 or 0 #=> -5
-0 == False #=> True
-2 == True #=> False
-1 == True #=> True
+0 and 2 # => 0
+-5 or 0 # => -5
+0 == False # => True
+2 == True # => False
+1 == True # => True
# negate with not
not True # => False
@@ -129,12 +130,12 @@ not False # => True
# You can find the length of a string
len("This is a string") # => 16
-#String formatting with %
-#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.
+# String formatting with %
+# 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.
x = 'apple'
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.
# 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
-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
-input_string_var = raw_input("Enter some data: ") # Returns the data as a string
-input_var = input("Enter some data: ") # Evaluates the data as python code
+input_string_var = raw_input(
+ "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
# Note: In python 3, input() is deprecated and raw_input() is renamed to input()
# 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
# 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
"yahoo!" if 3 > 2 else 2 # => "yahoo!"
-
# Lists store sequences
li = []
# You can start with a prefilled list
other_li = [4, 5, 6]
# Add stuff to the end of a list with append
-li.append(1) # li is now [1]
-li.append(2) # li is now [1, 2]
-li.append(4) # li is now [1, 2, 4]
-li.append(3) # li is now [1, 2, 4, 3]
+li.append(1) # li is now [1]
+li.append(2) # li is now [1, 2]
+li.append(4) # li is now [1, 2, 4]
+li.append(3) # li is now [1, 2, 4, 3]
# 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
-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
li[0] # => 1
@@ -230,21 +231,21 @@ li[2:] # => [4, 3]
# Omit the end
li[:3] # => [1, 2, 4]
# Select every second entry
-li[::2] # =>[1, 4]
+li[::2] # =>[1, 4]
# 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
# li[start:end:step]
# 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
-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.
# 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
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
# Check for existence in a list with "in"
-1 in li # => True
+1 in li # => True
# Examine the length with "len()"
-len(li) # => 6
-
+len(li) # => 6
# Tuples are like lists but are immutable.
tup = (1, 2, 3)
-tup[0] # => 1
+tup[0] # => 1
tup[0] = 3 # Raises a TypeError
# You can do all those list thingies on tuples too
-len(tup) # => 3
-tup + (4, 5, 6) # => (1, 2, 3, 4, 5, 6)
-tup[:2] # => (1, 2)
-2 in tup # => True
+len(tup) # => 3
+tup + (4, 5, 6) # => (1, 2, 3, 4, 5, 6)
+tup[:2] # => (1, 2)
+2 in tup # => True
# 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
-d, e, f = 4, 5, 6 # you can leave out the parentheses
+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
# 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
-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
empty_dict = {}
@@ -290,33 +289,33 @@ empty_dict = {}
filled_dict = {"one": 1, "two": 2, "three": 3}
# Look up values with []
-filled_dict["one"] # => 1
+filled_dict["one"] # => 1
# 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.
# Your results might not match this exactly.
# 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.
# 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"
-"one" in filled_dict # => True
-1 in filled_dict # => False
+"one" in filled_dict # => True
+1 in filled_dict # => False
# Looking up a non-existing key is a KeyError
-filled_dict["four"] # KeyError
+filled_dict["four"] # KeyError
# Use "get()" method to avoid the KeyError
-filled_dict.get("one") # => 1
-filled_dict.get("four") # => None
+filled_dict.get("one") # => 1
+filled_dict.get("four") # => None
# The get method supports a default argument when the value is missing
-filled_dict.get("one", 4) # => 1
-filled_dict.get("four", 4) # => 4
+filled_dict.get("one", 4) # => 1
+filled_dict.get("four", 4) # => 4
# note that filled_dict.get("four") is still => None
# (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", 6) # filled_dict["five"] is still 5
-
# Sets store ... well sets (which are like lists but can contain no duplicates)
empty_set = set()
# 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
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
-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
-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 &
other_set = {3, 4, 5, 6}
-filled_set & other_set # => {3, 4, 5}
+filled_set & other_set # => {3, 4, 5}
# 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 -
-{1, 2, 3, 4} - {2, 3, 5} # => {1, 4}
+{1, 2, 3, 4} - {2, 3, 5} # => {1, 4}
# Do set symmetric difference with ^
{1, 2, 3, 4} ^ {2, 3, 5} # => {1, 4, 5}
# 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
-{1, 2} <= {1, 2, 3} # => True
+{1, 2} <= {1, 2, 3} # => True
# Check for existence in a set with in
-2 in filled_set # => True
-10 in filled_set # => False
+2 in filled_set # => True
+10 in filled_set # => False
####################################################
-## 3. Control Flow
+# 3. Control Flow
####################################################
# Let's just make a variable
@@ -377,12 +375,11 @@ some_var = 5
# 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.
+elif some_var < 10: # This elif clause is optional.
print "some_var is smaller than 10."
-else: # This is optional too.
+else: # This is optional too.
print "some_var is indeed 10."
-
"""
For loops iterate over lists
prints:
@@ -438,12 +435,12 @@ try:
# Use "raise" to raise an error
raise IndexError("This is an index error")
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):
- pass # Multiple exceptions can be handled together, if required.
-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
-finally: # Execute under all circumstances
+ pass # Multiple exceptions can be handled together, if required.
+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
+finally: # Execute under all circumstances
print "We can clean up resources here"
# 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
def add(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
-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
-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
@@ -473,21 +471,26 @@ add(y=6, x=5) # Keyword arguments can arrive in any order.
def varargs(*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
# keyword args, as well, which will be interpreted as a dict by using **
def keyword_args(**kwargs):
return kwargs
+
# 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
def all_the_args(*args, **kwargs):
print args
print kwargs
+
+
"""
all_the_args(1, 2, a=3, b=4) prints:
(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.
args = (1, 2, 3, 4)
kwargs = {"a": 3, "b": 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(*args, **kwargs) # equivalent to foo(1, 2, 3, 4, a=3, b=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(*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
# by expanding them with * and ** respectively
@@ -509,58 +513,64 @@ def pass_all_the_args(*args, **kwargs):
print varargs(*args)
print keyword_args(**kwargs)
+
# Function Scope
x = 5
+
def set_x(num):
# Local var x not the same as global variable x
- x = num # => 43
- print x # => 43
+ x = num # => 43
+ print x # => 43
+
def set_global_x(num):
global x
- print x # => 5
- x = num # global var x is now set to 6
- print x # => 6
+ print x # => 5
+ x = num # global var x is now set to 6
+ print x # => 6
+
set_x(43)
set_global_x(6)
+
# Python has first class functions
def create_adder(x):
def adder(y):
return x + y
+
return adder
+
add_10 = create_adder(10)
-add_10(3) # => 13
+add_10(3) # => 13
# There are also anonymous functions
-(lambda x: x > 2)(3) # => True
-(lambda x, y: x ** 2 + y ** 2)(2, 1) # => 5
+(lambda x: x > 2)(3) # => True
+(lambda x, y: x ** 2 + y ** 2)(2, 1) # => 5
# There are built-in higher order functions
-map(add_10, [1, 2, 3]) # => [11, 12, 13]
-map(max, [1, 2, 3], [4, 2, 1]) # => [4, 2, 3]
+map(add_10, [1, 2, 3]) # => [11, 12, 13]
+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
[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.
{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.
class Human(object):
-
# A class attribute. It is shared by all instances of this class
species = "H. sapiens"
@@ -575,7 +585,6 @@ class Human(object):
# Initialize property
self.age = 0
-
# An instance method. All methods take "self" as the first argument
def say(self, msg):
return "{0}: {1}".format(self.name, msg)
@@ -611,45 +620,46 @@ class Human(object):
# Instantiate a class
i = Human(name="Ian")
-print i.say("hi") # prints out "Ian: hi"
+print i.say("hi") # prints out "Ian: hi"
j = Human("Joel")
print j.say("hello") # prints out "Joel: hello"
# Call our class method
-i.get_species() # => "H. sapiens"
+i.get_species() # => "H. sapiens"
# Change the shared attribute
Human.species = "H. neanderthalensis"
-i.get_species() # => "H. neanderthalensis"
-j.get_species() # => "H. neanderthalensis"
+i.get_species() # => "H. neanderthalensis"
+j.get_species() # => "H. neanderthalensis"
# Call the static method
-Human.grunt() # => "*grunt*"
+Human.grunt() # => "*grunt*"
# Update the property
i.age = 42
# Get the property
-i.age # => 42
+i.age # => 42
# Delete the property
del i.age
i.age # => raises an AttributeError
-
####################################################
-## 6. Modules
+# 6. Modules
####################################################
# You can import modules
import math
+
print math.sqrt(16) # => 4
# You can get specific functions from a module
from math import ceil, floor
+
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.
# Warning: this is not recommended
@@ -657,9 +667,11 @@ from math import *
# You can shorten module names
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
from math import sqrt
+
math.sqrt == m.sqrt == sqrt # => True
# 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
# defines a module.
import math
+
dir(math)
+
# If you have a Python script named math.py in the same
# folder as your current script, the file math.py will
# be loaded instead of the built-in Python module.
@@ -679,7 +693,7 @@ dir(math)
####################################################
-## 7. Advanced
+# 7. Advanced
####################################################
# Generators
@@ -693,6 +707,7 @@ def double_numbers(iterable):
for i in iterable:
double_arr.append(i + i)
+
# Running the following would mean we'll double all values first and return all
# of them back to be checked by our condition
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:
break
+
# We could instead use a generator to "generate" the doubled value as the item
# is being requested
def double_numbers_generator(iterable):
for i in iterable:
yield i + i
+
# 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
# 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
# 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:
print(x) # prints -1 -2 -3 -4 -5 to console/terminal
# 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)
print(gen_to_list) # => [-1, -2, -3, -4, -5]
-
# Decorators
# in this example beg wraps say
# Beg will call say. If say_please is True then it will change the returned
# message
from functools import wraps
+
def beg(target_function):
@wraps(target_function)
def wrapper(*args, **kwargs):
@@ -749,11 +766,13 @@ def beg(target_function):
return wrapper
+
@beg
def say(say_please=False):
msg = "Can you buy me a beer?"
return msg, say_please
+
print say() # Can you buy me a beer?
print say(say_please=True) # Can you buy me a beer? Please! I am poor :(
```