Python Files, Write, Append

To create a new file, or to overwrite existing one, use "w" as second argument:

f = open("external.txt", "w")

f.write("Line One")
f.write("Second One")
f.write("Third One")

f.close()

Result: 

Line OneSecond OneThird One

To evade concatenation, add "\n" at the end of every new line:

f = open("external.txt", "w")

f.write("Line One \n")
f.write("Second One \n")
f.write("Third One \n")

f.close()

Result: 

Line One 
Second One 
Third One 

If you need to add new content, without destruction of previous lines, use "a" as second argument:

f = open("external_2.txt", "a")

f.write("One More Time \n")
f.write("One More Time \n")
f.write("One More Time \n")

f.close()

Content of external_2.txt after we run code from above two times:

One More Time 
One More Time 
One More Time 
One More Time 
One More Time 
One More Time 

Sometimes we will need to delete files and folders. About that, in next tutorial.