Python - Coin Flip Streaks, returning double as much probability-CodePudding

I'm a beginner, new both to coding and to Python and I'm using the book "Automate the boring stuff with Python" to learn; one of the practice projects of the first chapters is the following:

Write a program to find out how often a streak of six heads or a streak of six tails comes up in a randomly generated list of heads and tails. Your program breaks up the experiment into two parts: the first part generates a list of randomly selected 'heads' and 'tails' values, and the second part checks if there is a streak in it. Put all of this code in a loop that repeats the experiment 10,000 times so we can find out what percentage of the coin flips contains a streak of six heads or tails in a row.

My programm returns exactly double as much percentage as it should. (Expected: 79-80%, returned 159%). I've tried to fix my code by comparing it with the other replies I've found but, since I've used a different approach, I still don't understand why this happens, as everything looks right.

import random

Total = []  # Defines the list in which there will be all of the throws

Throw = ("H", "T")  # Cases

for x in range(10000):  # Repeats the 100 throws 10 000 times
    for i in range(100):
        Total.append(random.choice(Throw))  # Adds a random throw to the list "Total";

Join = " ".join(Total)  # Creates a string to easily count the groups of T and H

N_T = Join.count("T T T T T T")  # Counts the Numbers of groups of six Tails
N_H = Join.count("H H H H H H")  # Counts the Numbers of groups of six Heads

print('Chance of streak: %s%%' % ((N_H   N_T) / 100))  # Probability

I hope this wasn't a dumb question... Thank you for your help.

CodePudding user response：

You need to set borders for your search terms, like this:

N_T = Join.count("H T T T T T T H")  # Counts the Numbers of groups of six Tails
N_H = Join.count("T H H H H H H T")  # Counts the Numbers of groups of six Heads

because otherwise what would happen if you have the following sequence:

"T T T T T T T T T T T T"

It can find your pattern multiple times in that bigger sequence, which leads to more hits than 100%, which of course is plausible in that case.