Acerca de Python

A continuación se presenta un tutorial con los conceptos básicos de Python que necesitas saber para usar oTree.

La forma más fácil de ejecutar este archivo es en IDLE (que generalmente se incluye en la instalación de Python).

Hay muchos otros buenos tutoriales de Python en línea, pero ten en cuenta que parte del material cubierto en esos tutoriales no es necesario para la programación en oTree específicamente.

Archivo de tutorial

Una versión descargable está aquí.

# Comments start with a # symbol.

####################################################
## 1. Basics
####################################################

# integer
3

# float (floating-point number)
3.14

# Math is what you would expect
1 + 1  # => 2
8 - 1  # => 7
10 * 2  # => 20
35 / 5  # => 7.0

# Enforce precedence with parentheses
(1 + 3) * 2  # => 8

# Boolean Operators
# Note they are
True and False # => False
False or True # => True

# negate with not
not True  # => False
not False  # => True

# Equality is ==
1 == 1  # => True
2 == 1  # => False

# Inequality is !=
1 != 1  # => False
2 != 1  # => True

# More comparisons
1 < 10  # => True
1 > 10  # => False
2 <= 2  # => True
2 >= 2  # => True

# A string (text) is created with " or '
"This is a string."
'This is also a string.'

# Strings can be added too!
"Hello " + "world!"  # => "Hello world!"

# None means an empty/nonexistent value
None  # => None


####################################################
## 2. Variables, lists, and dicts
####################################################

# print() displays the value in your command prompt window
print("I'm Python. Nice to meet you!") # => I'm Python. Nice to meet you!

# Variables
some_var = 5
some_var  # => 5

# Lists store sequences
li = []

# 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(3)    # li is now [1, 2, 3]

# Access a list like you would any array
# in Python, the first list index is 0, not 1.
li[0]  # => 1
# Assign new values to indexes that have already been initialized with =
li[0] = 42
li # => [42, 2, 3]


# You can add lists
other_li = [4, 5, 6]
li + other_li   # => [42, 2, 3, 4, 5, 6]

# Get the length with "len()"
len(li)   # => 6

# Here is a prefilled dictionary
filled_dict = dict(name='Lancelot', quest="To find the holy grail", favorite_color="Blue")

# Look up values with []
filled_dict['name']   # => 'Lancelot'

# Check for existence of keys in a dictionary with "in"
'name' in filled_dict   # => True
'age' in filled_dict   # => False

# set the value of a key with a syntax similar to lists
filled_dict["age"] = 30  # now, filled_dict["age"] => 30

####################################################
## 3. Control Flow
####################################################

# Let's just make a variable
some_var = 5

# Here is an if statement.
# 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.
    print("some_var is smaller than 10.")
else:           # This is optional too.
    print("some_var is indeed 10.")

"""
SPECIAL NOTE ABOUT INDENTING
In Python, you must indent your code correctly, or it will not work.
All lines in a block of code must be aligned along the left edge.
When you're inside a code block (e.g. "if", "for", "def"; see below),
you need to indent by 4 spaces.

Examples of wrong indentation:

if some_var > 10:
print("bigger than 10." # error, this line needs to be indented by 4 spaces


if some_var > 10:
    print("bigger than 10.")
 else: # error, this line needs to be unindented by 1 space
    print("less than 10")

"""


"""
For loops iterate over lists
prints:
    1
    4
    9
"""
for x in [1, 2, 3]:
    print(x*x)

"""
"range(number)" returns a list of numbers
from zero to the given number MINUS ONE

the following code prints:
    0
    1
    2
    3
"""
for i in range(4):
    print(i)


####################################################
## 4. Functions
####################################################

# Use "def" to create new functions
def add(x, y):
    print('x is', x)
    print('y is', y)
    return x + y

# Calling functions with parameters
add(5, 6)   # => prints out "x is 5 and y is 6" and returns 11


####################################################
## 5. List comprehensions
####################################################

# We can use list comprehensions to loop or filter
numbers = [3,4,5,6,7]
[x*x for x in numbers]  # => [9, 16, 25, 36, 49]

numbers = [3, 4, 5, 6, 7]
[x for x in numbers if x > 5]   # => [6, 7]

####################################################
## 6. Modules
####################################################

# You can import modules
import random
print(random.random()) # random real between 0 and 1

Créditos: El tutorial de esta página está adaptado de Learn Python in Y Minutes, y se publica bajo la misma licencia.