How to open plain text files in Python?

Quick start

read()

file = open('hello.txt')
txt = file.read()

print(txt)

hello there!
this is a plain text file
with 3 lines

readlines()

file = open('hello.txt')
lines = file.readlines()

print(lines)

['hello there!\n', 'this is a plain text file\n', 'with 3 lines']

List all the files in one folder

# os is a Python module that makes it possible to interact with the operating system
# we will use it to list all the files that sit in a specific folder
import os

# This is where our plain text files are that we want to open
path = './plain-text-files/'

# This is the list that we want to fill with files
files = []

# os.listdir() returns a list containing the names of the files in this folder
for filename in os.listdir(path):
    
    # os.path.join() glues the path + filename together
    file_path = os.path.join(path, filename)
    
    print('---')
    print('filename                :', filename)
    print('file_path               :', file_path)
    
    # os.path.isfile() checks if this is a "regular file"
    if os.path.isfile(file_path) == True:
    
        # if that is the case (is True)
        # then we add the file_path to the list called "files"
        # we use .append() for this, which is a Python way to add items to lists
        files.append(file_path) 
        print('file_path added to list : YES')
        
    else:
        print('file_path added to list : NO')
        
        

---
filename                : .ipynb_checkpoints
file_path               : ./plain-text-files/.ipynb_checkpoints
file_path added to list : NO
---
filename                : hello-xpub.txt
file_path               : ./plain-text-files/hello-xpub.txt
file_path added to list : YES
---
filename                : hello-world.txt
file_path               : ./plain-text-files/hello-world.txt
file_path added to list : YES

files

['./test/hello-xpub.txt', './test/hello-world.txt']

Open a list of files in Python

read()

for file_path in files:
    
    print('---')
    print('file_path :', file_path)
    
    file = open(file_path, 'r') # 'r' stands for 'reading', it means that we only open this file for reading its content
    print('file      :', file)
    
    # Open the file and read() its content as a single string
    txt = file.read()
    print('txt       :', txt)
    

---
file_path : ./plain-text-files/hello-xpub.txt
file      : <_io.TextIOWrapper name='./plain-text-files/hello-xpub.txt' mode='r' encoding='UTF-8'>
txt       : hello XPUB
?
?
?
---
file_path : ./plain-text-files/hello-world.txt
file      : <_io.TextIOWrapper name='./plain-text-files/hello-world.txt' mode='r' encoding='UTF-8'>
txt       : hello world!
!
!
!

readlines()

for file_path in files:
    
    print('---')
    print('file_path :', file_path)
    
    file = open(file_path, 'r') # 'r' stands for 'reading', it means that we only open this file for reading its content
    print('file      :', file)
    
    # Open the file and readlines() its content as a list of lines
    lines = file.readlines()
    print('lines     :', lines)

---
file_path : ./plain-text-files/hello-xpub.txt
file      : <_io.TextIOWrapper name='./plain-text-files/hello-xpub.txt' mode='r' encoding='UTF-8'>
lines     : ['hello XPUB\n', '?\n', '?\n', '?']
---
file_path : ./plain-text-files/hello-world.txt
file      : <_io.TextIOWrapper name='./plain-text-files/hello-world.txt' mode='r' encoding='UTF-8'>
lines     : ['hello world!\n', '!\n', '!\n', '!\n']