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Objets de fichier en Python

Un objet fichier nous permet d'utiliser l'accès et de manipuler tous les fichiers accessibles par l'utilisateur. On peut lire et écrire de tels fichiers. Lorsqu'une opération sur un fichier échoue pour une raison liée aux E/S, l'exception IOError est levée. Cela inclut les situations dans lesquelles l'opération n'est pas définie pour une raison quelconque, comme seek() sur un périphérique tty ou l'écriture d'un fichier ouvert en lecture. Les fichiers ont les méthodes suivantes :
    ouvrir(): Opens a file in given access mode. 
     open(file_address access_mode)
    Examples of accessing a file: A file can be opened with a built-in function called open(). This function takes in the file’s address and the access_mode and returns a file object. There are different types of access_modes: 
      r:   Opens a file for reading only   r+:   Opens a file for both reading and writing   w:   Opens a file for writing only   w+:   Open a file for writing and reading.   a:   Opens a file for appending   a+:   Opens a file for both appending and reading
    When you add 'b' to the access modes you can read the file in binary format rather than the default text format. It is used when the file to be accessed is not in text. lire([taille]) : It reads the entire file and returns it contents in the form of a string. Reads at most size bytes from the file (less if the read hits EOF before obtaining size bytes). If the size argument is negative or omitted read all data until EOF is reached. Python 
    # Reading a file f = open(__file__ 'r') #read() text = f.read(10) print(text) f.close()
    readline([taille]) : It reads the first line of the file i.e till a newline character or an EOF in case of a file having a single line and returns a string. If the size argument is present and non-negative it is a maximum byte count (including the trailing newline) and an incomplete line may be returned. An empty string is returned only when EOF is encountered immediately. Python 
    # Reading a line in a file f = open(__file__ 'r') #readline() text = f.readline(20) print(text) f.close()
    lignes de lecture ([indice de taille]) : It reads the entire file line by line and updates each line to a list which is returned.Read until EOF using readline() and return a list containing the lines thus read. If the optional sizehint argument is present instead of reading up to EOF whole lines totalling approximately sizehint bytes (possibly after rounding up to an internal buffer size) are read. Python 
    # Reading a file f = open(__file__ 'r') #readline() text = f.readlines(25) print(text) f.close()
    écrire (chaîne) : It writes the contents of string to the file. It has no return value. Due to buffering the string may not actually show up in the file until the flush() or close() method is called. Python 
    # Writing a file f = open(__file__ 'w') line = 'Welcome Geeksn' #write() f.write(line) f.close()
    Plus d'exemples dans différents modes : Python 
    # Reading and Writing a file f = open(__file__ 'r+') lines = f.read() f.write(lines) f.close()
    Python 
    # Writing and Reading a file f = open(__file__ 'w+') lines = f.read() f.write(lines) f.close()
    Python 
    # Appending a file f = open(__file__ 'a') lines = 'Welcome Geeksn' f.write(lines) f.close()
    Python 
    # Appending and reading a file f = open(__file__ 'a+') lines = f.read() f.write(lines) f.close()
    lignes d'écriture (séquence) : It is a sequence of strings to the file usually a list of strings or any other iterable data type. It has no return value. Python 
    # Writing a file f = open(__file__ 'a+') lines = f.readlines() #writelines() f.writelines(lines) f.close()
    dire() : It returns an integer that tells us the file object’s position from the beginning of the file in the form of bytes Python 
    # Telling the file object position f = open(__file__ 'r') lines = f.read(10) #tell() print(f.tell()) f.close()
    chercher (décalage de_où) : It is used to change the file object’s position. Offset indicates the number of bytes to be moved. from_where indicates from where the bytes are to be moved. Python 
    # Setting the file object position f = open(__file__ 'r') lines = f.read(10) print(lines) #seek() print(f.seek(22)) lines = f.read(10) print(lines) f.close()
    flush() : Flush the internal buffer like stdio‘s fflush(). It has no return value. close() automatically flushes the data but if you want to flush the data before closing the file then you can use this method. Python 
    # Clearing the internal buffer before closing the file f = open(__file__ 'r') lines = f.read(10) #flush() f.flush() print(f.read()) f.close()
    fichierno() : Returns the integer file descriptor that is used by the underlying implementation to request I/O operations from the operating system. Python 
    # Getting the integer file descriptor f = open(__file__ 'r') #fileno() print(f.fileno()) f.close()
    isatty() : Returns True if the file is connected to a tty(-like) device and False if not. Python 
    # Checks if file is connected to a tty(-like) device f = open(__file__ 'r') #isatty() print(f.isatty()) f.close()
    suivant() : It is used when a file is used as an iterator. The method is called repeatedly. This method returns the next input line or raises StopIteration at EOF when the file is open for reading( behaviour is undefined when opened for writing). Python 
    # Iterates over the file f = open(__file__ 'r') #next() try: while f.next(): print(f.next()) except: f.close()
    tronquer([taille]) : Truncate the file's size. If the optional size argument is present the file is truncated to (at most) that size. The size defaults to the current position. The current file position is not changed. Note that if a specified size exceeds the file's current size the result is platform-dependent: possibilities include that the file may remain unchanged increase to the specified size as if zero-filled or increase to the specified size with undefined new content. Python 
    # Truncates the file f = open(__file__ 'w') #truncate() f.truncate(10) f.close()
    fermer() : Used to close an open file. A closed file cannot be read or written any more. Python 
    # Opening and closing a file f = open(__file__ 'r') #close() f.close()
    Attributs:
      fermé: renvoie un booléen indiquant l'état actuel de l'objet fichier. Il renvoie vrai si le fichier est fermé et faux lorsque le fichier est ouvert. codage: L'encodage utilisé par ce fichier. Lorsque des chaînes Unicode sont écrites dans un fichier, elles seront converties en chaînes d'octets en utilisant cet encodage. mode: Le mode E/S du fichier. Si le fichier a été créé à l'aide de la fonction intégrée open(), ce sera la valeur du paramètre mode. nom: Si l'objet fichier a été créé en utilisant open() le nom du fichier. nouvelles lignes: Un objet fichier qui a été ouvert en mode nouvelle ligne universelle possède cet attribut qui reflète la convention de nouvelle ligne utilisée dans le fichier. La valeur de cet attribut est 'r' 'n' 'rn' None ou un tuple contenant tous les types de nouvelle ligne vus. espace logiciel : It is a boolean that indicates whether a space character needs to be printed before another value when using the print statement. Python 
      f = open(__file__ 'a+') print(f.closed) print(f.encoding) print(f.mode) print(f.newlines) print(f.softspace)
Article connexe : Lire et écrire dans des fichiers texte en Python Référence: https://docs.python.org/2.4/lib/bltin-file-objects.html