Python

 # This program demonstrates string functions.
 
 
 def main():
     string = "Hello"
 
     print("string: " + string)
     print("string.lower(): " + string.lower())
     print("string.upper(): " + string.upper())
     print("string.find('e'): " + str(string.find('e')))
     print("len(string): " + str(len(string)))
     print("string.replace('H', 'j'): " + string.replace('H', 'j')) 
     print("string[::-1]: " + string[::-1])
     print("string[2:4]: " + string[2:4])
     print("string.strip('H'): " + string.strip('H'))
 
     name = "Bob"
     value = 123.456
     print("string.format(): {0} earned ${1:.2f}".format(name, value))
 
 
 main()

 # This program creates a file, adds data to the file, displays the file,
 # appends more data to the file, displays the file, and then deletes the file.
 # It will not run if the file already exists.
 #
 # References:
 #     https://www.mathsisfun.com/temperature-conversion.html
 #     https://en.wikibooks.org/wiki/Python_Programming
 
 
 import os
 import sys
 
 
 def calculate_fahrenheit(celsius):
     fahrenheit = celsius * 9 / 5 + 32    
     return fahrenheit
 
 
 def create_file(filename):
     try:
         file = open(filename, "w")
         file.write("Celsius,Fahrenheit\n")
         for celsius in range(0, 51):
             fahrenheit = calculate_fahrenheit(celsius)
             file.write("{:.1f},{:.1f}\n".format(celsius, fahrenheit))
         file.close()
     except:
         print("Error creating", filename)
         print(sys.exc_info()[1])
 
 
 def read_file(filename):
     try:
         file = open(filename, "r")
         for line in file:
             line = line.strip()
             print(line)
         file.close()
         print()
     except:
         print("Error reading", filename)
         print(sys.exc_info()[1])
 
 
 def append_file(filename):
     try:
         file = open(filename, "a")
         for celsius in range(51, 101):
             fahrenheit = calculate_fahrenheit(celsius)
             file.write("{:.1f},{:.1f}\n".format(celsius, fahrenheit))
         file.close()
     except:
         print("Error appending to", filename)
         print(sys.exc_info()[1])
 
 
 def delete_file(filename):
     try:
         os.remove(filename)
     except:
         print("Error deleting", filename)
         print(sys.exc_info()[1])
 
 
 def main():
     filename = "~file.txt"
 
     if os.path.isfile(filename):
         print("File already exists.")
     else:
         create_file(filename)
         read_file(filename)
         append_file(filename)
         read_file(filename)
         delete_file(filename)
         
 
 main()