Python files / directories part16

Python files / directories part16

• 1.
  Prof. Neeraj Bhargava VishalDutt Department of Computer Science, School of Engineering & System Sciences MDS University, Ajmer
• 2.
   The FileObjects provides a set of methods or functions to perform various tasks in the file.  Two common tasks are reading a file and writing into a file. The write() Method  The write() method writes any string to an open file.  It is important to note that Python strings can have binary data and not just text. Reading and Writing Files
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   The write()method does not add a newline character ('n') to the end of the string . Syntax: fileObject.write(string) Example # Open a file fo = open("foo.txt", "wb") fo.write( "Python is a great language.nYeah its great!!n") # Close opend file fo.close()
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   "a" -Append - will append to the end of the file  "w" - Write - will overwrite any existing content Example 1: f = open("demofile2.txt", "a") f.write("Now the file has more content!") f.close() Example 2: f = open("demofile3.txt", "w") f.write("Woops! I have deleted the content!") f.close()
• 5.
  Create a NewEmpty File To create a new file in Python, use the open() method, with one of the following parameters:  "x" - Create - will create a file, returns an error if the file exist f = open("myfile.txt", "x") Result: a new empty file is created!
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  The read() Method The read() method reads a string from an open file. Syntax: fileObject.read([count])  Here passed parameter is the number of bytes to be read from the opened file.  This method starts reading from the beginning of the file and if count is missing, then it tries to read as much as possible, maybe until the end of file.
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  Example: f = open("demofile.txt","r") print(f.read()) Example: # Open a file fo = open(“demofile.txt", "r+") str = fo.read(10); print "Read String is : ", str # Close opend file fo.close() Hello! Welcome to demofile.txt This file is for testing purposes. Good Luck! demofile.text
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  Read Lines  Youcan return one line by using the readline() method: Example: f = open("demofile.txt", "r") print(f.readline())  By calling readline() two times, you can read the two first lines: Hello! Welcome to demofile.txt
• 9.
  Questions  Illustrate Filereading in Python/  Illustrate Writing into the file in Python.  How can you print line by line from a file using loops? Explain with Example.