Added a few lines about truthiness, how lists can contain arbitrary data types, how you can unpack both tuples and lists, using

This commit is contained in:
Michael Lee 2013-06-29 21:35:11 -07:00
parent 2431545594
commit cc3dc30518

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@ -93,6 +93,16 @@ not False #=> True
# None is an object
None #=> None
# Don't use the equality `==` symbol to compare objects to None
# Use `is` instead
"etc" is None #=> False
None is None #=> True
# None, 0, and empty strings/lists all evaluate to False.
# All other values are True
0 == False #=> True
"" == False #=> True
####################################################
## 2. Variables and Collections
@ -159,6 +169,9 @@ li.extend(other_li) # Now li is [1, 2, 3, 4, 5, 6]
# Examine the length with len
len(li) #=> 6
# Note: lists can contain arbitrary values
li2 = [1, "Hello", [[], "Hi", 5,]]
# Tuples are like lists but are immutable.
tup = (1, 2, 3)
tup[0] #=> 1
@ -170,7 +183,7 @@ tup + (4, 5, 6) #=> (1, 2, 3, 4, 5, 6)
tup[:2] #=> (1, 2)
2 in tup #=> True
# You can unpack tuples 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
# Tuples are created by default if you leave out the parentheses
d, e, f = 4, 5, 6
@ -268,6 +281,18 @@ for animal in ["dog", "cat", "mouse"]:
# You can use % to interpolate formatted strings
print "%s is a mammal" % animal
"""
`range(number)` returns a list of numbers
from zero to the given number
prints:
0
1
2
3
"""
for i in range(4):
print i
"""
While loops go until a condition is no longer met.
prints:
@ -350,6 +375,8 @@ add_10(3) #=> 13
# There are also anonymous functions
(lambda x: x > 2)(3) #=> True
rectangle_area = lambda a, b: a * b
print rectangle_area(3, 4) #=> 12
# There are built-in higher order functions
map(add_10, [1,2,3]) #=> [11, 12, 13]
@ -359,6 +386,9 @@ filter(lambda x: x > 5, [3, 4, 5, 6, 7]) #=> [6, 7]
[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]
# You can also use dictionary comprehensions
{i: add_10(i) for i in [1, 2, 3]} #=> {1: 11, 2: 12, 3: 13}
####################################################
## 5. Classes
####################################################
@ -374,7 +404,8 @@ class Human(object):
# Assign the argument to the instance's name attribute
self.name = name
# An instance method. All methods take self as the first argument
# An instance method. All methods take self as the first argument,
# which refers to the instance of this class
def say(self, msg):
return "%s: %s" % (self.name, msg)
@ -407,6 +438,33 @@ j.get_species() #=> "H. neanderthalensis"
# Call the static method
Human.grunt() #=> "*grunt*"
####################################################
## 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 floor3.7) #=> 3.0
# You can import all functions from a module.
# Warning: this is not recommended
from math import *
# You can shorten module names
import math as m
math.sqrt(16) == m.sqrt(16) #=> True
# Python modules are just ordinary python files. You
# can write your own, and import them.
```
## Further Reading
@ -417,3 +475,7 @@ Still up for more? Try:
* [Dive Into Python](http://www.diveintopython.net/)
* [The Official Docs](http://docs.python.org/2.6/)
* [Hitchhiker's Guide to Python](http://docs.python-guide.org/en/latest/)
Python has a huge amount of modules within the standard library. See the
[official documentation](http://docs.python.org/2/library/index.html) or
[Python Module of the Week](http://pymotw.com/2/) for more.