[Python tutorial] 18. File handling

File Handling

File Open: open(filename, mode)

• "r" - Read, Default value, error if the file does not exist
• "a" - Append, creates the file if it does not exist
• "w" - Write, creates the file if it does not exist
• "x" - Create specified file, returns an error if the file exists
• "t" - Default value. Text mode
• "b" - Binary mode (e.g. images)

Syntax

f = open("demofile.txt", "rt")

Read

demofile.txt

Hello! Welcome to demofile.txt
This file is for testing purposes.
Good Luck!

Read characters

f = open("D:\\myfiles\welcome.txt", "r")
print(f.read())
print(f.read(5)) # Return the 5 first characters of the file

Read Lines: readline()

f = open("demofile.txt", "r")
print(f.readline())

# Loop through the file line by line:
for x in f:
  print(x)
Close Files # always close file

File Write

Write to an Existing File

• "a": append to the end of the file
• "w": overwrite any existing content

f = open("demofile2.txt", "a")
f.write("Now the file has more content!")
f.close()

f = open("demofile3.txt", "w")
f.write("Woops! I have deleted the content!")
f.close()

Create a New File

• "x"
• "a"
• "a"

f = open("myfile.txt", "x")

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

Delete File

• os 모듈 필요

import os
os.remove("demofile.txt")

Check if file exists

if os.path.exists("demofile.txt"):
  os.remove("demofile.txt")
else:
  print("The file does not exist")

Delete Folder

import os
os.rmdir("myfolder")
# only remove empty folders