Files

Change the current directory

• Absolute path :

import os
os.chdir("C:/tests python")

• Relative path :

import os
os.chdir("../../relative_dir")

Open a file

mon_fichier = open("fichier.txt", "r")

Modes

‘r’	Read
‘w’	Write (file is created if it doesn’t exist, file with the same name is erased)
‘a’	Apend (file is created if it doesn’t exist)
‘t’	Option : open as text. Ex : open("file.txt", "rt")
‘b’	Option : open as binary. Ex : open("file.txt", "rb")

Close a file

mon_fichier.close()

Read the whole content of a file

mon_fichier = open("fichier.txt", "r")
mon_fichier.read()

Write to a file

• Write a string

mon_fichier = open("fichier.txt", "w")
mon_fichier.write("Premier test d'écriture dans un fichier via Python")

• Write other data types

  TODO see os package for more infos

Safer way to use files with the with keyword

-> automatically closes the file when the operation is finished

with open('fichier.txt', 'r') as mon_fichier:
    texte = mon_fichier.read()

Save objects to files with pickle

• Use the Pickler class
• dump method to save the object
• Write to the file in binary ‘b’ mode

import pickle

score = {
    "joueur 1":    5,
    "joueur 2":   35,
    "joueur 3":   20,
    "joueur 4":    2,
}

with open('donnees', 'wb') as fichier:
    mon_pickler = pickle.Pickler(fichier)
    mon_pickler.dump(score)

Retrieve objects from files with pickle

• Use the Unpickler class
• load method to load the object from the file
• Open the file in binary ‘b’ mode

import pickle

with open('donnees', 'rb') as fichier:
    mon_depickler = pickle.Unpickler(fichier)
    score_recupere = mon_depickler.load()