I am following https://automatetheboringstuff.com/2e/chapter8 

CHAPTER 8. Input validation. 

In terminal, do pip3 install --user pyinputplus . 
Then in Python, do 
import pyinputplus as pyip

inputStr() is like input(). 

x = pyip.inputNum()

inputNum() ensures the user enters a number and returns an int or float, depending on if the number has a decimal point in it

inputChoice() Ensures the user enters one of the provided choices

inputMenu() Is similar to inputChoice(), but provides a menu with numbered or lettered options. 

inputDatetime() Ensures the user enters a date and time. 

inputYesNo() Ensures the user enters a “yes” or “no” response. 

inputBool() Is similar to inputYesNo(), but takes a “True” or “False” response and returns a Boolean value. 

inputEmail() Ensures the user enters a valid email address. 

x = pyip.inputEmail()

inputFilepath() Ensures the user enters a valid file path and filename, and can optionally check that a file with that name exists. 

inputPassword() is like the built-in input(), but displays * characters as the user types so that passwords, or other sensitive information, aren’t displayed on the screen. This works in terminal but not in IDLE. 

limit = 2 means they only get 2 tries and timeout=10 means they only get 10 seconds! Cool. 
response = pyip.inputNum(timeout=10,default="NA") ## It still waits til you answer though. 

CHAPTER 9. Reading and writing files. 

The beginning of chapter 9 covers paths. This seems unnecessary to me. As we saw before, you can use 
import os 
os.getcwd() 
os.chdir("/Users/rickpaikschoenberg/Desktop/Python") 

os.path.getsize("pig.py") ## says how big the file is. Cool. 
os.listdir() ## lists files. 
for filename in os.listdir(): 
	print(filename + " " + str(os.path.getsize(filename))) 
You can use glob() to list only certain files. 

## Writing to files. 
from pathlib import Path 
p = Path("new.txt") 
p.write_text("test it out now") 
p.read_text() 

## Better to use open() 
newfile = open("new.txt") 
newfile.read() 
newfile.readlines() ## One string for each new line. 
newfile = open("new.txt","a") ## a for append mode. w for write mode for overwriting the file. 
newfile.write("\nthis is the 2nd line.\n") 
newfile.close() 
newfile = open("new.txt") 
print(newfile.readlines()) 
newfile.close() 

## Save variables with pprint(). 
import pprint
cats = [{'name': 'Zophie', 'desc': 'chubby'}, {'name': 'Pooka', 'desc': 'fluffy'}]
fileObj = open('myCats.py', 'w')
fileObj.write('cats = ' + pprint.pformat(cats) + '\n')
fileObj.close()