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Open , Read and Close , Print , Split , Form an orderly queue , Repeat , Just Use a Loop!

 


Reading From a File 


Once we've got data into a file, wouldn't it be just splendid to load it back into our program to use again?
Yes. Yes is the answer you're looking for.


Open 

👉 The code to load from a file is pretty similar to that for writing. The command is open instead of read, and the permissions are slightly different.


f = open("filenames.list", "r") 

 

Read and Close

👉 In this example, the permission 'r' means 'read only'. Now we load the contents of the file into a variable using the read function. Next, close the file to free up the RAM used to store it.


f = open("filenames.list", "r")
contents = f.read()
f.close()

Print

👉 Finally output the contents of the 'contents' variable to test that it worked.

f = open("filenames.list", "r")
contents = f.read()
f.close()
print(contents)

Split


Bringing everything in in one go is fine, but it would be much more useful to have it as separate items so we can examine it more easily.

👉 To do this, use the .split() function in the second to last line. This splits the string into a list of individual elements.

f = open("filenames.list", "r")
contents = f.read()
f.close()
contents = contents.split() #added split here
print(contents) 
One At A Time

Form an orderly queue

Reading all the data at once is fine, reading one item at a time works slightly differently.

It uses the .readline() function.

👉 The code below reads one line from the file.

f = open("filenames.list","r")
contents = f.readline()
print(contents)
f.close()
 
Repeat

To read more than one line, we repeat the command.

👉 The strip() function removes the default new line from each print, which would cause an empty line between each line from the file.

f = open("filenames.list","r")
contents = f.readline().strip()
print(contents)
contents = f.readline().strip()
print(contents)
contents = f.readline().strip()
print(contents)
contents = f.readline().strip()
print(contents)
f.close()


Just Use a Loop!

👉 If you're screaming 'LOOP! USE A FREAKING LOOP, MAN!' at the screen right about now.

Your wish is my command.

f = open("filenames.list","r")
while True:
  contents = f.readline().strip()
  
  if contents == "":
    break
  #The last line in the file will be a blank
  #We break the loop if the line read is a blank
  print(contents)
  # Moved the print after the break so it won't output the final blank line.
f.close()






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