Labels: Python, Keyboard Input, Files

Ref: Python Files I/O https://www.tutorialspoint.com/python/python_files_io.htm

Keyboard Input

• raw_input
  raw_input([prompt]): reads one line from standard input and returns it as a string. For example:

Enter your input: Hello Python
Received input is :  Hello Python

• input
  input([prompt]): assumes the input is a valid Python expression and returns the evaluated result to you. For example:

Enter your input: [x*5 for x in range(2,10,2)]
Recieved input is :  [10, 20, 30, 40]

Files

• file object

• open function
  Creates a file object, which would be utilized to call other support methods associated with it.

file object = open(file_name [, access_mode][, buffering])

file_name: The file_name argument is a string value that contains the name of the file that you want to access.
access_mode: The access_mode determines the mode in which the file has to be opened, i.e., read, write, append, etc. A complete list of possible values is given below in the table. This is optional parameter and the default file access mode is read (r).
buffering: If the buffering value is set to 0, no buffering takes place. If the buffering value is 1, line buffering is performed while accessing a file. If you specify the buffering value as an integer greater than 1, then buffering action is performed with the indicated buffer size. If negative, the buffer size is the system default(default behavior).

• close function
  A file object flushes any unwritten information and closes the file object.

fileObject.close();

• write function
  The write() method writes any string to an open file.
  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()

• read function
  The read() method reads a string from an open file.
  Syntax

fileObject.read([count]);

count 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.

• File position
• tell(): returns the current position within the file.
• seek(offset[, from]): changes the current file position. The offset argument indicates the number of bytes to be moved. The from argument specifies the reference position from where the bytes are to be moved.
• Example

# Open a file
fo = open("foo.txt", "r+")
str = fo.read(10);
print "Read String is : ", str
# Check current position
position = fo.tell();
print "Current file position : ", position
# Reposition pointer at the beginning once again
position = fo.seek(0, 0);
str = fo.read(10);
print "Again read String is : ", str
# Close opend file
fo.close()

• rename() function
  Needed to import Python os module.

import os

rename() takes two arguments, the current filename and the new filename.
Syntax

os.rename(current_file_name, new_file_name)

Example

import os
# Rename a file from test1.txt to test2.txt
os.rename( "test1.txt", "test2.txt" )

• remove() function
  Needed to import Python os module.
  remove() deletes files by supplying the name of the file to be deleted as the argument.
  Syntax

os.remove(file_name)

Example

import os
# Delete file test2.txt
os.remove("text2.txt")

Dictionaries