I'm trying to learn python because it might come in handy to know at some point in the future. The way I'm learning is by using this online python interpreter along with this tutorial.
Every programming tutorial conventionally starts with the "Hello, World!" program. Here it is in Python:
PROGRAM
>print("Hello World!")
OUTPUT
Hello World!
Makes sense so far. So, the next thing you might wonder is how do we assign a value to a variable in Python? It is quite simple, here's an example of assigning the literal string value of "Hello World!" to a variable called testVar: testVar = "Hello World!".
The next thing to learn is how to operate with values. Here's an example of that:
PROGRAM
>print(5 + 8)
print("14" + " the string")
print(13//2)
print(9756 % 10)
print(2 ** 3)
OUTPUT
13
14 the string
6
6
8
What's interesting to note is that Python has native operators for floor division (\\) and exponents (**), which I think is quite nice because we don't have to go running off writing our own functions for these operations. Of course we can do a re-assignment of a variable while performing some operation in one concise step as well:
PROGRAM
>test = 8
test **= 2
print(test)
OUTPUT
64
Interestingly, there's no ++ or -- operators like there is in most languages:
PROGRAM
>test = 0
test ++
print(test)
OUTPUT
File "main.py", line 2
test ++
^
SyntaxError: invalid syntax
Of course we can get around this easily by using the += operator:
PROGRAM
>test = 0
test += 1
print(test)
OUTPUT
1
The next thing the tutorial introduces us to is a method for accepting and working with user input:
PROGRAM
>someInput = input("Enter some text here:")
print("\n" + someInput)
Entering the string this is some input for STDIN:
OUTPUT
Enter some text here:
this is some input
To make a single line comment in the source code we can use # (the pound sign). We can also make multi-line comments:
PROGRAM
># hey there I'm a sexy one-line comment
'''
This comment
is spread
over multiple lines
and ignored by the interpreter
'''
print("The bastard","took all my m&ms!")
OUTPUT
The bastard took all my m&ms!
The next thing introduced is implicit type conversion:
PROGRAM
>someInt = 2
someReal = 2.3
print(someInt + someReal)
result = someInt + someReal
print(type(result))
OUTPUT
4.3
<class 'float'>
As we can see, adding an integer and a float together results in a float.
We can do explict type conversion as well:
PROGRAM
>print(bool("I wonder what will happen"))
print(bool(''))
print(float("2.657"))
OUTPUT
True
False
2.657
As you can see, I was curious about what would happen if I converted an empty and non-empty string value to a boolean. Python won't throw an error, but will return True for any non-emtpy string value and False for an empty string. Neato.
Python has your regular integer and float types but also has a complex numeric type for the more mathematically inclined:
PROGRAM
>print(2j + 3j)
print(complex("5j"))
OUTPUT
5j
5j
After learning the basics of the language, the tutorial moves us on to learn about the data structures that are native to Python. The first one we learn about is the "list" structure:
PROGRAM
>list = [1, 2, 3, "this is a list"]
print(list)
list[2] = 4.5
print(list[-2])
print(list[1])
OUTPUT
[1, 2, 3, 'this is a list']
4.5
2
One interesting thing to note is that we can go backwards in a list starting from the last item of the list using the index -1.
The next structure that we are introduced to is similar to a list, however, unlike a list, it's immutable. This type of data structure is called a "tuple".
PROGRAM
>tuple = (1, 2, 3)
print(tuple[1])
tuple[0] = "haha"
print(tuple)
OUTPUT
2
Traceback (most recent call last):
File "main.py", line 3, in <module>
tuple[0] = "haha"
TypeError: 'tuple' object does not support item assignment
As you can see, trying to assign a value to an element in a tuple results in a run-time error.
This section of the tutorial introduces the interesting operator del.
PROGRAM
>num = 10.0
string = "This is a test string"
t1 = (3, 8, 12, 69)
l1 = ["apples", "tofu", "oranges", "tea"]
print(num, string, t1, l1)
del num
del string
del t1
del l1
print(num)
OUTPUT
10.0 This is a test string (3, 8, 12, 69) ['apples', 'tofu', 'oranges', 'tea']
Traceback (most recent call last):
File "main.py", line 13, in <module>
print(num)
NameError: name 'num' is not defined
I played around with del to see if it could delete things like numbers, strings, tuples, and lists, and it can certainly handle that. I'm not sure what del is really good for yet but I'm sure it has it's uses.
Next up is the good old programming standyby: the string.
PROGRAM
>test = "here there be dragons"
test1 = '''this
is
another
string'''
print(test1)
print(test[3] + test[-1])
# slicing in python
print(test[1:4])
list = ["this", "is", "cool"]
print(list[:-1])
print("the thing" * 5)
OUTPUT
this
is
another
string
es
ere
['this', 'is']
the thingthe thingthe thingthe thingthe thing
We can define, concatenate, and slice strings! I was curious if the slicing syntax worked for lists as well and it does, so I'm assuming it works for tuples too. I also like the ability to repeat a string by using the * operator. Cool.
"Sets" are next. Here's some cool stuff we can do with them:
PROGRAM
>set1 = {1, 2, 3}
set2 = {3, 4, 5}
# union operation
print(set1 | set2)
# subtraction
print(set2 - set1)
# intersection
print(set1 & set2)
# add multiple elements at once
set1.update([4, 10, 12])
print(set1)
# add one element
set2.add("ComPuTeR")
print(set2)
# remove one element
set1.remove(1)
print(set1)
OUTPUT
{1, 2, 3, 4, 5}
{4, 5}
{3}
{1, 2, 3, 4, 10, 12}
{3, 4, 5, 'ComPuTeR'}
{2, 3, 4, 10, 12}
I am really enjoying the fact that sets are so readily available to be worked with in Python. Most often we don't directly deal with the notion of a set in a programming language (and we use arrays as a substitute) so the fact that python supports this is very awesome indeed!
Next up, "Dictionaries"!
PROGRAM
>dict = {"wine": "quite a lovely drink", "PI": 3.14, (1, 2, 3): 100}
print(dict["wine"])
print(dict["PI"])
print(dict[(1, 2, 3)])
dict[(1, 2, 3)] = "this is quite odd"
print(dict)
del dict[(1, 2, 3)]
print(dict)
OUTPUT
quite a lovely drink
3.14
100
{'wine': 'quite a lovely drink', 'PI': 3.14, (1, 2, 3): 'this is quite odd'}
{'wine': 'quite a lovely drink', 'PI': 3.14}
As you can see, dictionaries are quite friendly in python as well! I was curious if you could use any value as a key in a dictionary and, as you can see above, you can! Deleting keys is easy too!
The next task is to get familiar with the range function.
PROGRAM
># define a range
r = range(1, 6)
# use a range to create a list, tuple, set, or dictionary!
print(list(r))
print(tuple(r))
print(set(r))
print(dict.fromkeys(r, "test"))
print(dict.fromkeys(range(90, 100, 2)))
OUTPUT
[1, 2, 3, 4, 5]
(1, 2, 3, 4, 5)
{1, 2, 3, 4, 5}
{1: 'test', 2: 'test', 3: 'test', 4: 'test', 5: 'test'}
{90: None, 92: None, 94: None, 96: None, 98: None}
Lists, tuples, sets, and dictionaries can all be instantiated from a range. You can choose the amount to "step" by as the third argument to the range function. As you can see in the code above, creating a dictionary from a range where the value of each dictionary item is not specified is totally valid as well!
if...else in python:
PROGRAM
>if 5 > 6:
print('Hi')
elif 100 <= 99:
print('Why me?')
else:
print("Well you're here now.")
print(not(True and False))
print(not True)
OUTPUT
Well you're here now.
True
False
So, we can control program flow with an if statement and use all the usual logical (and, or, not) and comparison (==, <=, >=, <, >, !=) operators.
Here's a while loop:
PROGRAM
>keepLooping = True
loopTimes = 0
while keepLooping:
loopTimes += 1
print("I am looping",loopTimes,"times!")
if loopTimes == 10:
keepLooping = False
OUTPUT
I am looping 1 times!
I am looping 2 times!
I am looping 3 times!
I am looping 4 times!
I am looping 5 times!
I am looping 6 times!
I am looping 7 times!
I am looping 8 times!
I am looping 9 times!
I am looping 10 times!
Simple enough. The loop continues to execute as long as the conditional expression evaluates to True.
Traversing over any iterable sequence (list, tuple, set, dictionary, or range) using a for loop:
PROGRAM
>breakfast = ["eggs", "bacon", "hashbrowns"]
for item in breakfast:
print(item)
for i in range(2, 5):
print(i)
dict = {"one": 1, "two": 2, "three": 3}
for key in dict:
print("key:", key, "value:", dict[key]))
OUTPUT
eggs
bacon
hashbrowns
2
3
4
key: one value: 1
key: two value: 2
key: three value: 3
Sweet.
On to Functions!
PROGRAM
>def func():
pass
def func1(one, two):
return one + two
print(func())
print(func1(8, 6))
OUTPUT
None
14
Functions in python can return values, accept arguments, and execute arbitrary code. It is interesting to note that we can use the pass keyword to basically make a block of python code do nothing. Python also has a concept of something called a "lambda" function. We can use it on a filter or map operation.
PROGRAM
>l = [101, 89.6, 3j, 4.5, 2, 14 / 3]
integers = list(filter(lambda i: type(i) is int, l))
print(integers)
l1 = list(map(lambda i: i / 2, l))
print(l1)
OUTPUT
[101, 2]
[50.5, 44.8, 1.5j, 2.25, 1.0, 2.3333333333333335]
I defined a list called l and assigned some values to it. I then used the filter function, only selecting items that were of the type int. I also called the map function to return a list of all the items of l divided by 2! Lambda functions aren't strictly necessary here but I'm assuming it's good practice to use them in this case.
Python also has support for object orientation.
PROGRAM
>class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def tostring(self):
return "This person's name is: " + self.name + " and their age is: " + str(self.age) + "!"
p = Person("Kelan", 28)
print(p.tostring())
OUTPUT
This person's name is: Kelan and their age is: 28!
Here I've defined a simple Person class that has two attributes, a name and an age and I've defined a method of that class that uses those attributes.
There is of course more to learn in regards to Python but I think we have a good basis on which to build out a project from. I've taken inspiration for a problem to work on with Python from a book I possess from my college days: Data Structures and Algorithms by Michael Goodrich, Roberto Tamassia, and Michael Goldwasser. Problem P-2.31 on page 100 reads:
Write a Java program to simulate an ecosystem containing two types of creatures, bears and fish. The ecosystem consists of a river, which is modeled as a relatively large array. Each cell of the array should contain an
Animalobject, which can be aBearobject, aFishobject, or null. In each time step, based on a random process, each animal either attempts to move into an adjacent array cell or stay where it is. If two animals of the same type are about to collide in the same cell, then they stay where they are, but they create a new instance of that type of animal, which is placed in a random empty (i.e., previously null) cell in the array. If a bear and a fish collide, however, then the fish dies (i.e., it disappears). Use actual object creation, via the new operator, to model the creation of new objects, and provide a visualization of the array after each time step.
This problem was intended to be solved ind Java but we can adapt it for learning Python as well. As you can see, the authors are trying to hammer home object orientation as well, so we will use some object oriented features of the Python language in our solution.
So, we need to simulate the river that the bears and fish live in, so we can create a River, Animal, Fish, and Bear class. We can use that handy pass keyword to avoid having to define bodies for these classes for the time being.
>class River:
class Animal:
pass
class Bear(Animal):
pass
class Fish(Animal):
pass
def __init__(self):
self.river_array = []
You can run this code and it executes just fine. In Python you can easily define a class within another class. Here I'm defining the Animal, Bear, and Fish class within the River class because only the River should need access to new instances of Fish and Bear. Now to begin with, we should probably be able to instantiate a River object by passing the River's size as an argument to the constructor method. Here I added some code to do that. I'm using a list to represent the river and instantiating all the elements as either Bear, Fish, or the special None objects, based off a random number generator.
PROGRAM
>import random
class Animal:
pass
class Bear(Animal):
def __repr__(self):
return "Bear"
class Fish(Animal):
def __repr__(self):
return "Fish"
def getAnimal(i):
r = random.randint(0, 2)
if r == 0:
return Bear()
elif r == 1:
return Fish()
else:
return None
def make_river(river_size):
return list(map(getAnimal, range(0, river_size)))
# TESTING
print(make_river(5))
print(make_river(10))
print(make_river(2))
print(make_river(8))
OUTPUT
[Bear, Bear, Bear, Fish, None]
[None, Bear, Bear, Bear, None, None, Fish, Fish, Fish, None]
[None, Bear]
[None, Bear, None, Bear, Bear, Fish, None, Bear]
So, now that I can generate randomly sized "rivers" populated with different Animal or None objects, I think the next thing to do is code what happens when the animals start moving around and breeding or eating each other.
PROGRAM
>import random
class Animal:
pass
class Bear(Animal):
def __repr__(self):
return "Bear"
class Fish(Animal):
def __repr__(self):
return "Fish"
def getAnimal(i):
r = random.randint(0, 2)
if r == 0:
return Bear()
elif r == 1:
return Fish()
else:
return None
def make_river(river_size):
return list(map(getAnimal, range(0, river_size)))
def none_indexes(l):
index = 0
none_list = []
for i in l:
if i == None:
none_list.append(index)
index += 1
return none_list
def choose_random_item(l):
if len(l) > 1:
return l[random.randint(0, len(l) - 1)]
elif len(l) == 1:
return l[0]
return None
def move_animals(river):
i = 0
while i < len(river):
if issubclass(type(river[i]), Animal):
if random.randint(0, 1) == 0:
if random.randint(0, 1) == 0:
if i < len(river) - 1:
if type(river[i]) == type(river[i + 1]):
print(river[i], "at index:", i, "met another", river[i + 1], "while moving right. Time to breed!")
rni = choose_random_item(none_indexes(river))
if rni != None:
if type(river[i]) == Bear:
river[rni] = Bear()
print(river[rni], "spawned at index:", str(rni) + ".")
else:
river[rni] = Fish()
print(river[rni], "spawned at index:", str(rni) + ".")
else:
print("There is no more room to spawn new animals in the river!")
elif type(river[i]) == Bear and type(river[i + 1]) == Fish:
river[i + 1] = river[i]
river[i] = None
print("Bear moved right from index:", i, "and ate Fish at index:", str(i + 1) + ".")
i += 1
elif type(river[i]) == Fish and type(river[i + 1]) == Bear:
river[i] = None
print("Fish swam right from index:", i, "and was eaten by Bear at index:", str(i + 1) + ".")
else:
print(river[i], "at index:", i, "moved right.")
river[i + 1] = river[i]
river[i] = None
i += 1
else:
print(river[i],"at index:", i, "tried to move right but is out of space, so they stayed put.")
else:
if i > 0:
if type(river[i]) == type(river[i - 1]):
print(river[i], "at index:", i, "met another", river[i - 1], "while moving left. Time to breed!")
rni = choose_random_item(none_indexes(river))
if rni != None:
if type(river[i]) == Bear:
river[rni] = Bear()
print(river[rni], "spawned at index:", str(rni) + ".")
else:
river[rni] = Fish()
print(river[rni], "spawned at index:", str(rni) + ".")
else:
print("There is no more room to spawn new animals in the river!")
elif type(river[i]) == Bear and type(river[i - 1]) == Fish:
river[i - 1] = river[i]
river[i] = None
print("Bear moved left from index:", i, "and ate fish at index:", str(i - 1) + ".")
elif type(river[i]) == Fish and type(river[i - 1]) == Bear:
river[i] = None
print("Fish swam left from index:", i, "and was eaten by Bear at index:", str(i - 1) + ".")
else:
print(river[i], "at index:", i, "moved left.")
river[i - 1] = river[i]
river[i] = None
else:
print(river[i],"at index:", i, "tried to move left but is out of space, so they stayed put.")
else:
print(river[i],"at index:", i, "chose not to move.")
i += 1
time_steps = 10
river_size = 20
river = make_river(river_size)
for i in range(0, time_steps):
print("River state:")
print(river)
move_animals(river)
print(river)
OUTPUT
River state:
[Fish, Bear, None, None, Fish, Fish, Bear, None, None, Bear, Fish, None, Bear, Bear, Bear, Fish, None, Bear, None, Fish]
Fish at index: 0 chose not to move.
Bear at index: 1 chose not to move.
Fish at index: 4 chose not to move.
Fish at index: 5 chose not to move.
Bear at index: 6 chose not to move.
Bear at index: 9 chose not to move.
Fish swam left from index: 10 and was eaten by Bear at index: 9.
Bear at index: 12 chose not to move.
Bear at index: 13 met another Bear while moving left. Time to breed!
Bear spawned at index: 2.
Bear at index: 14 chose not to move.
Fish at index: 15 chose not to move.
Bear at index: 17 chose not to move.
Fish at index: 19 chose not to move.
River state:
[Fish, Bear, Bear, None, Fish, Fish, Bear, None, None, Bear, None, None, Bear, Bear, Bear, Fish, None, Bear, None, Fish]
Fish at index: 0 chose not to move.
Bear at index: 1 met another Bear while moving right. Time to breed!
Bear spawned at index: 18.
Bear at index: 2 chose not to move.
Fish at index: 4 moved left.
Fish at index: 5 moved left.
Bear at index: 6 moved right.
Bear at index: 9 moved right.
Bear at index: 12 moved left.
Bear at index: 13 chose not to move.
Bear moved right from index: 14 and ate Fish at index: 15.
Bear at index: 17 chose not to move.
Bear at index: 18 chose not to move.
Fish at index: 19 chose not to move.
River state:
[Fish, Bear, Bear, Fish, Fish, None, None, Bear, None, None, Bear, Bear, None, Bear, None, Bear, None, Bear, Bear, Fish]
Fish swam right from index: 0 and was eaten by Bear at index: 1.
Bear at index: 1 chose not to move.
Bear at index: 2 chose not to move.
Fish at index: 3 chose not to move.
Fish at index: 4 chose not to move.
Bear at index: 7 chose not to move.
Bear at index: 10 chose not to move.
Bear at index: 11 chose not to move.
Bear at index: 13 chose not to move.
Bear at index: 15 moved left.
Bear at index: 17 chose not to move.
Bear at index: 18 chose not to move.
Fish at index: 19 chose not to move.
River state:
[None, Bear, Bear, Fish, Fish, None, None, Bear, None, None, Bear, Bear, None, Bear, Bear, None, None, Bear, Bear, Fish]
Bear at index: 1 chose not to move.
Bear at index: 2 met another Bear while moving left. Time to breed!
Bear spawned at index: 16.
Fish at index: 3 chose not to move.
Fish at index: 4 chose not to move.
Bear at index: 7 moved right.
Bear at index: 10 met another Bear while moving right. Time to breed!
Bear spawned at index: 5.
Bear at index: 11 chose not to move.
Bear at index: 13 met another Bear while moving right. Time to breed!
Bear spawned at index: 0.
Bear at index: 14 met another Bear while moving left. Time to breed!
Bear spawned at index: 6.
Bear at index: 16 moved left.
Bear at index: 17 chose not to move.
Bear at index: 18 met another Bear while moving left. Time to breed!
Bear spawned at index: 7.
Fish at index: 19 tried to move right but is out of space, so they stayed put.
River state:
[Bear, Bear, Bear, Fish, Fish, Bear, Bear, Bear, Bear, None, Bear, Bear, None, Bear, Bear, Bear, None, Bear, Bear, Fish]
Bear at index: 0 chose not to move.
Bear at index: 1 chose not to move.
Bear at index: 2 chose not to move.
Fish at index: 3 met another Fish while moving right. Time to breed!
Fish spawned at index: 12.
Fish swam right from index: 4 and was eaten by Bear at index: 5.
Bear at index: 5 met another Bear while moving right. Time to breed!
Bear spawned at index: 4.
Bear at index: 6 met another Bear while moving right. Time to breed!
Bear spawned at index: 16.
Bear at index: 7 met another Bear while moving right. Time to breed!
Bear spawned at index: 9.
Bear at index: 8 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 9 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 10 chose not to move.
Bear at index: 11 chose not to move.
Fish at index: 12 chose not to move.
Bear moved left from index: 13 and ate fish at index: 12.
Bear at index: 14 moved left.
Bear at index: 15 chose not to move.
Bear at index: 16 chose not to move.
Bear at index: 17 met another Bear while moving right. Time to breed!
Bear spawned at index: 14.
Bear moved right from index: 18 and ate Fish at index: 19.
River state:
[Bear, Bear, Bear, Fish, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, None, Bear]
Bear at index: 0 chose not to move.
Bear at index: 1 met another Bear while moving left. Time to breed!
Bear spawned at index: 18.
Bear at index: 2 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Fish at index: 3 chose not to move.
Bear at index: 4 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 5 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 6 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 7 chose not to move.
Bear at index: 8 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 9 chose not to move.
Bear at index: 10 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 11 chose not to move.
Bear at index: 12 chose not to move.
Bear at index: 13 chose not to move.
Bear at index: 14 chose not to move.
Bear at index: 15 chose not to move.
Bear at index: 16 chose not to move.
Bear at index: 17 chose not to move.
Bear at index: 18 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 19 chose not to move.
River state:
[Bear, Bear, Bear, Fish, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear]
Bear at index: 0 tried to move left but is out of space, so they stayed put.
Bear at index: 1 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 2 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Fish at index: 3 chose not to move.
Bear moved left from index: 4 and ate fish at index: 3.
Bear at index: 5 chose not to move.
Bear at index: 6 met another Bear while moving right. Time to breed!
Bear spawned at index: 4.
Bear at index: 7 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 8 chose not to move.
Bear at index: 9 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 10 chose not to move.
Bear at index: 11 chose not to move.
Bear at index: 12 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 13 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 14 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 15 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 16 chose not to move.
Bear at index: 17 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 18 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 19 chose not to move.
River state:
[Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear]
Bear at index: 0 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 1 chose not to move.
Bear at index: 2 chose not to move.
Bear at index: 3 chose not to move.
Bear at index: 4 chose not to move.
Bear at index: 5 chose not to move.
Bear at index: 6 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 7 chose not to move.
Bear at index: 8 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 9 chose not to move.
Bear at index: 10 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 11 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 12 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 13 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 14 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 15 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 16 chose not to move.
Bear at index: 17 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 18 chose not to move.
Bear at index: 19 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
River state:
[Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear]
Bear at index: 0 chose not to move.
Bear at index: 1 chose not to move.
Bear at index: 2 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 3 chose not to move.
Bear at index: 4 chose not to move.
Bear at index: 5 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 6 chose not to move.
Bear at index: 7 chose not to move.
Bear at index: 8 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 9 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 10 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 11 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 12 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 13 chose not to move.
Bear at index: 14 chose not to move.
Bear at index: 15 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 16 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 17 chose not to move.
Bear at index: 18 chose not to move.
Bear at index: 19 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
River state:
[Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear]
Bear at index: 0 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 1 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 2 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 3 chose not to move.
Bear at index: 4 chose not to move.
Bear at index: 5 chose not to move.
Bear at index: 6 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 7 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 8 chose not to move.
Bear at index: 9 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 10 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 11 chose not to move.
Bear at index: 12 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 13 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 14 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 15 chose not to move.
Bear at index: 16 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 17 met another Bear while moving left. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 18 met another Bear while moving right. Time to breed!
There is no more room to spawn new animals in the river!
Bear at index: 19 tried to move right but is out of space, so they stayed put.
[Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear, Bear]
As you can see, because bears can eat fish but not vice-versa, as the simulation plays out the bears eventually outbreed and eat all the fish!
Of course there is more to learn in regards to python, but I think solving this problem gives us a good basis to starting coding from.
Happy coding!