importing random

>>> import random
>>> dir(random)
['BPF', 'LOG4', 'NV_MAGICCONST', 'RECIP_BPF', 'Random', 'SG_MAGICCONST',
'SystemRandom', 'TWOPI', '_Sequence', '_Set', '__all__', '__builtins__',
'__cached__', '__doc__', '__file__', '__loader__', '__name__', '__package__',
'__spec__', '_accumulate', '_acos', '_bisect', '_ceil', '_cos', '_e', '_exp',
'_inst', '_log', '_os', '_pi', '_random', '_repeat', '_sha512', '_sin',
'_sqrt', '_test', '_test_generator', '_urandom', '_warn', 'betavariate',
'choice', 'choices', 'expovariate', 'gammavariate', 'gauss', 'getrandbits',
'getstate', 'lognormvariate', 'normalvariate', 'paretovariate', 'randint',
'random', 'randrange', 'sample', 'seed', 'setstate', 'shuffle', 'triangular',
'uniform', 'vonmisesvariate', 'weibullvariate']
>>> print(random.randint.__doc__)
Return random integer in range [a, b], including both end points.

Generating Pseudorandom Integers We will use this to roll a single die and then to shake dem bonz.

>>> random.randint(1,6)
2
>>> random.randint(1,6)
1
>>> random.randint(1,6)
4
>>> random.randint(1,6)
6
>>> random.randint(1,6)
2
>>> (random.randint(1,6),random.randint(1,6))
(2, 5)
>>> (random.randint(1,6),random.randint(1,6))
(3, 3)

Shuffling a List Pass a list to random.shuffle and it will be shuffled using the Fischer-Yates algorithm.

>>> x = [1,2,3,4,5,6]
>>> random.shuffle(x)
>>> x
[1, 4, 6, 2, 5, 3]
>>> random.shuffle(x)
>>> x
[6, 4, 3, 1, 2, 5]

Random Sampling from a List Here we pluckk out a single element at random.

>>> random.choice(x)
6
>>> random.choice(x)
1
>>> random.choice(x)
5

Now we pick three elements without replacement. >>> random.sample(x, 3) [3, 2, 4] >>> random.sample(x, 3) [5, 4, 1] >>> random.sample(x, 3) [3, 6, 5]

Flipping a Coin: Do this by making a random choice from the list ["H", "T"].

Roll an exotic die from an RPG, say 20-sided. This is just the tool.

Making a Magic 8 Ball

Here is a list with its replies.

replies = ["As I see it, yes.", "Ask again later.", "Better not tell you now.", "Cannot predict now.", "Concentrate and ask again.", "Don't count on it.", "It is certain.", "It is decidedly so."] 

Our program will ignore the question entered by the user and it will spit out one of its cryptic replies.

import random
question = input("Enter your question:   ")
replies = ["As I see it, yes.", "Ask again later.", "Better not tell you now.", "Cannot predict now.", "Concentrate and ask again.", "Don't count on it.", "It is certain.", "It is decidedly so."]
print("The answer to your question")
print(question)
print (f"is: {random.choice(replies)}")

unix> python eightball.py 
Enter your question:   Is is raining outside?
The answer to your question
Is is raining outside?
is: Don't count on it.

Generating Uniform Variates Here we get a random floating-point number in the interval [0, 1).

>>> random.random()
0.13212661879466792
>>> random.random()
0.8637168910820039
>>> random.random()
0.982909339902225

We can do this for any range we'd like as follows.

>>> random.uniform(0,10)
8.579159479118163
>>> random.uniform(0,10)
3.8694437072194834
>>> random.uniform(0,10)
6.754578729500322
>>> random.uniform(0,10)
1.6187927982936734
>>> random.uniform(0,10)
9.929038622798107

• strings This iterator walks through a string one character at a time in index order.
• lists and tuples Their iterators walk through one element at a time in index order.
• sets The iterator walks through the set in no particular order.
• dictionaries The iterator walks the keys of a dictionary one key at a time in no particular order.
• file objects The iterator walks through a file one line at a time.

Here are some other iterables.

• range objects
• dictionary_keys object
• dictionary_values object

We will do tons of examples.

enumerate and reversed are very handy for altering the behavior of iterators.