text_file = open("File.txt", "w") #Creating a "txt" file. This will overwrite your old text values.
#If you want to overwrite: 
text_file.write("Hello!") #Deleted all the old texts in the "txt" file and just typed "Hello!" in it.
#To make it not overwrite:
text_file = open("File.txt", "r")

text = text_file.read() #Reading the contents of the "txt" file

new_text = "Hello!" #We are going to write "Hello" in the "txt" file

with open("File.txt", "w") as text_file: #Opening it as a "w" because we got the values from the txt file, and ready to overwrite with it
  text_file.write(text, new_text) #Writing the texts into the "txt" file
text_file.close #Closing the "txt" file