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# Taken from https://github.com/ehmatthes/pcc/releases/download/v1.0.0/beginners_python_cheat_sheet_pcc_all.pdf | |
### TYPES | |
my_boolean = True | |
my_string = "Hello, world!" | |
my_integer = 10 | |
my_long = 345L | |
my_float = 45.67 | |
my_complex = 3.14J | |
my_list = [ 1, 2, 3 ] | |
my_dictionary = { "foo": "bar", "moo": 1 } | |
my_tuple = ( 1, 2, 3 ) | |
### VARIABLES AND STRINGS | |
''' | |
Variables are used to store values. A string is a series of | |
characters, surrounded by single or double quotes. | |
''' | |
# Hello world | |
print( "Hello, world!" ) | |
# Hello world with a variable | |
msg = "Hello, world!" | |
print( msg ) | |
# Concatenation (combining strings) | |
first_name = "Albert" | |
last_name = "Einstein" | |
full_name = first_name + " " + last_name | |
print( full_name ) | |
### LISTS | |
''' | |
A list stores a series of items in a particular order. You | |
access items using an index, or within a loop | |
''' | |
# Make a list | |
bikes = [ "trek", "redline", "giant" ] | |
# Get the first item in a list | |
first_bike = bikes[0] | |
# Get the last item in a list | |
last_bike = bikes[-1] | |
# Looping through a list | |
for bike in bikes: | |
print( bike ) | |
# Adding items to a list | |
bikes = [] | |
bikes.append( "trek" ) | |
bikes.append( "redline" ) | |
bikes.append( "giant" ) | |
# Making numerical lists | |
squares = [] | |
for x in range( 1, 11 ): | |
squares.append( x ** 2 ) | |
# List comprehensions | |
squares = [ x ** 2 for x in range( 1, 11 ) ] | |
# Slicing a list | |
finishers = [ "sam", "bob", "ada", "bea" ] | |
first_two = finishers[0:2] | |
# Copying a list | |
copy_of_bikes = bikes[:] | |
### TUPLES | |
''' | |
Tuples are similar to lists, but the items in a tuple can't be | |
modified. | |
''' | |
# Making a tuple | |
dimensions = ( 1920, 1080 ) | |
### IF STATEMENTS | |
''' | |
If statements are used to test for particular conditions and | |
respond appropriately. | |
''' | |
# Conditional tests | |
x == 42 # is x equal to 42? | |
x != 42 # is x not equal to 42? | |
x > 42 # is x greater than 42? | |
x >= 42 # is x greater than or equal to 42? | |
x < 42 # is x less than 42? | |
x <= 42 # is x less than or equal to 42? | |
# Conditional test with lists | |
"trek" in bikes # is trek in bikes? | |
"surly" not in bikes # is surly not in bikes? | |
# Assigning boolean values | |
game_active = True | |
can_edit = False | |
# A simple if test | |
age = 21 | |
if age >= 18: | |
print( "You can vote!" ) | |
# if-elif-else statements | |
if age < 4: | |
ticket_price = 0 | |
elif age < 18: | |
ticket_price = 10 | |
else: | |
ticket_price = 15 | |
### DICTIONARIES | |
''' | |
Dictionaries store connections between pieces of | |
information. Each item in a dictionary is a key-value pair. | |
''' | |
# A simple dictionary | |
alien = { | |
"color": "green", | |
"points": 5 | |
} | |
# Accessing a value | |
print( "The alien's color is " + alien["color"] ) | |
# Adding a new key-value pair | |
alien["x_position"] = 0 | |
# Looping through all key-value pairs | |
fav_numbers = { "eric": 17, "ever": 4 } | |
for name, number in fav_numbers.items( ): | |
print( name + " loves " + str( number ) ) | |
# Looping through all the keys | |
for name in fav_numbers.keys( ): | |
print( name + " loves a number" ) | |
# Looping through all the values | |
for number in fav_numbers.values( ): | |
print( str( number ) + " is a favorite" ) | |
### USER INPUT | |
''' | |
Your programs can prompt the user for input. All input is | |
stored as a string. | |
''' | |
# Prompting for a value | |
#name = input( "What's your name? " ) | |
#print( "Hello, " + name + "!" ) | |
# Prompting for numerical input | |
age = input( "How old are you? " ) | |
age = int( age ) | |
pi = input( "What's the value of pi? " ) | |
pi = float( pi ) | |
### WHILE LOOPS | |
''' | |
A while loop repeats a block of code as long as a certain | |
condition is true. | |
''' | |
# A simple while loop | |
current_value = 1 | |
while current_value <= 5: | |
print( current_value ) | |
current_value += 1 | |
# Letting the user choose when to quit | |
msg = "" | |
while msg != "quit": | |
msg = input( "What's your message? " ) | |
print( msg ) | |
### FUNCTIONS | |
''' | |
Functions are named blocks of code, designed to do one | |
specific job. Information passed to a function is called an | |
argument, and information received by a function is called a | |
parameter. | |
''' | |
# A simple function | |
def greet_user( ): | |
print( "Hello!" ) | |
greet_user( ) | |
# Passing an argument | |
def greet_user( username ): | |
print( "Hello, " + username + "!" ) | |
greet_user( "Zeaga" ) | |
# Default values for parameters | |
def make_pizza ( topping = "bacon" ): | |
print( "Make a " + topping + " pizza!" ) | |
make_pizza( ) | |
make_pizza( "pepperoni" ) | |
# Returning a value | |
def add_numbers( x, y ): | |
return x + y | |
sum = add_numbers( 3, 5 ) | |
print( sum ) | |
### CLASSES | |
''' | |
A class defines the behavior of an object and the kind of | |
information an object can store. The information in a class | |
is stored in attributes, and functions that belong to a class | |
are called methods. A child class inherits the attributes and | |
methods from its parent class. | |
''' | |
# Creating a dog class | |
class Dog( object ): | |
def __init__( self, name ): | |
self.name = name | |
def sit( self ): | |
print( self.name + " is sitting." ) | |
my_dog = Dog( "Gena" ) | |
print( my_dog.name + " is a great dog!" ) | |
my_dog.sit( ) | |
# Inheritance | |
class SearchDog( Dog ): | |
def __init__( self, name ): | |
super( SearchDog, self ).__init__( name ) | |
def search( self ): | |
print( self.name + " is searching." ) | |
my_dog = SearchDog( "Kenaga" ) | |
print( my_dog.name + " is a search dog." ) | |
my_dog.sit( ) | |
my_dog.search( ) | |
### WORKING WITH FILES | |
''' | |
Your programs can read from files and write to files. Files | |
are opened in read mode ('r') by default, but can also be | |
opened in write mode ('w') and append mode ('a'). | |
''' | |
# Reading a file and storing its lines | |
filename = "siddhartha.txt" | |
with open( filename ) as file_object: | |
lines = file_object.readlines( ) | |
for line in lines: | |
print( line ) | |
# Writing to a file | |
filename = "journal.txt" | |
with open( filename, "w" ) as file_object: | |
file_object.write( "I love Python" ) | |
# Appending to a file | |
filename = "journal.txt" | |
with open( filename, "a" ) as file_object: | |
file_object.write( "\nI love programming." ) | |
### EXCEPTIONS | |
''' | |
Exceptions help you respond appropriately to errors that | |
are likely to occur. You place code that might cause an | |
error in the try block. Code that should run in response to | |
an error goes in the except block. Code that should run only | |
if the try block was successful goes in the else block. | |
''' | |
# Catching an exception | |
prompt = "How many tickets do you need?" | |
num_tickets = input( prompt + " " ) | |
try: | |
num_tickets = int( num_tickets ) | |
except ValueError: | |
print( "Please try again." ) | |
else: | |
print( "Your tickets are printing." ) | |
### INFINITE SKILLS | |
## If you had infinite programming skills, what would you build? | |
''' | |
As you're learning to program, it's helpful to think | |
about the real-world projects you'd like to create. It's | |
a good habit to keep an "ideas" notebook that you | |
can refer to whenever you want to start a new project. | |
If you haven't done so already, take a few minutes | |
and describe three projects you'd like to create. | |
''' | |
### ZEN OF PYTHON | |
## Simple is better than complex | |
''' | |
If you have a choice between a simple and a complex | |
solution, and both work, use the simple solution. Your | |
code will be easier to maintain, and it will be easier | |
for you and others to build on that code later on. | |
''' |
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