File Input Output¶

Text files¶

Text files are a simple way to save and retrieve data. They have the advantage of being human readable, so you can open a text file and see what has been saved.

The disadvantage of text files is that everything is save and read as strings. You will need to String Methods and data type converters to change the data back to the format you wish to use.

Reading text files¶

Read all the file¶

with open(r"python_files\names.txt", "r", encoding="utf-8") as file:
    data = file.read()
    
print(data)

Note:

"python_files\names.txt" → path to the text file
"r" → read mode
all values read from text files are strings

Read one line¶

with open(r"python_files\names.txt", "r", encoding="utf-8") as file:
    data = file.readline()
    
print(data)

Note:

"python_files\names.txt" → path to the text file
"r" → read mode
all values read from text files are strings

Read a set number of lines¶

with open(r"python_files\names.txt", "r", encoding="utf-8") as file:
    data = file.readlines(5)
    
print(data)

Note:

"python_files\names.txt" → path to the text file
"r" → read mode
all values read from text files are strings

Read the file into a list¶

with open(r"python_files\names.txt", "r", encoding="utf-8") as file:
    data = file.read().split("\n")
    
print(data)

Note:

"python_files\names.txt" → path to the text file
"r" → read mode
all values read from text files are strings

Writing text files¶

Writing to a text file will:

create a new text file if it doesn’t already exist
overwrite the text file if it does already exist

Write a variable to text file¶

value = "String that will be written to text file"

with open("python_files\save_variable.txt", "w") as file:
    file.write(value)

Note:

"python_files\save_file.txt" → path to the text file
"w" → write mode
all values written to text files are strings

Write a list to text file¶

This will write each list element on a new line.

values = ["Michelle", "Nicole", "Emma", "Justine", "Maria"]

with open("python_files\save_list.txt", "w") as file:
    for item in values:
        file.write(f"{item}\n")

Note:

"python_files\save_file.txt" → path to the text file
"w" → write mode
all values written to text files are strings

Pickle files¶

Python’s pickle module saves Python objects as binary files. This may seem limiting but remember that everything in Python is an object.

The advantage of using pickle to save is the object type is preserved. For example, if you save a dictionary, it will return as a dictionary when you load it.

The disadvantage of pickling is that the save file is in binary, so it is not human readable. You cannot open the file to see what has been saved.

Save a file (pickling)¶

import pickle

values = ["Michelle", "Nicole", "Emma", "Justine", "Maria"]

with open("python_files/save_file.pkl", "wb") as file:
    pickle.dump(values, file)

Note:

"python_files/save_file.pkl" → the path to the pickle file
wb → the file needs to write binary

Read a file (unpickle)¶

import pickle

with open("python_files\save_file.pkl", "rb") as file:
    values = pickle.load(file)
    
print(values)

Note:

"python_files/save_file.pkl" → the path to the pickle file
rb → the file needs to read binary