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diff --git a/getting_started_with_files/script.rst b/getting_started_with_files/script.rst index 259be80..22b5ddc 100644 --- a/getting_started_with_files/script.rst +++ b/getting_started_with_files/script.rst @@ -23,166 +23,289 @@ Script ------ -{{{ Show the slide containing title }}} +.. L1 -Hello Friends. Welcome to the tutorial on getting started with files. +{{{ Show the first slide containing title, name of the production +team along with the logo of MHRD }}} -{{{ Show the outline for this tutorial }}} +.. R1 -In this tutorial we shall learn to read files, and do some basic -actions on the file, like opening and reading a file, closing a -file, iterating through the file line-by-line, and appending the -lines of a file to a list. +Hello Friends and Welcome to the tutorial on "Getting started with files". -{{{ switch back to the terminal }}} +.. L2 -As usual, we start IPython, using +{{{ Show slide with objectives }}} + +.. R2 + +At the end of this tutorial, you will be able to, + + 1. Open a file. + #. Read the contents of the file line by line. + #. Read the entire content of file at once. + #. Append the lines of a file to a list. + #. Close the file. + +.. L3 + +{{{ switch to the terminal }}} :: - ipython -pylab + ipython -pylab + +.. R3 + +Open the terminal and start ipython + +.. R4 Let us first open the file, ``pendulum.txt`` present in ``/home/fossee/``. + +.. L4 :: - f = open('/home/fossee/pendulum.txt') + f = open('/home/fossee/pendulum.txt') -``f`` is called a file object. Let us type ``f`` on the terminal to +.. R5 + +Here ``f`` is called a file object. Let us type ``f`` on the terminal to see what it is. + +.. L5 :: - f + f + +.. R6 + +The file object shows the filepath and mode of the file which is open. +'r' stand for read only mode and 'w' stands for write mode. +As you can see, this file is open in read only mode. -The file object shows, the file which is open and the mode (read -or write) in which it is open. Notice that it is open in read only -mode, here. +.. L6 + +.. R7 We shall first learn to read the whole file into a single -variable. We use the ``read`` method of ``f`` to read, all the contents of the file -into the variable ``pend``. +variable. We use the ``read`` method to read all the contents of the file +into the variable, ``pend``. + +.. L7 :: - pend = f.read() + pend = f.read() + +.. R8 -Now, let us see what is in ``pend``, by typing +Now, let us see what ``pend`` contains, by typing ``print pend`` + +.. L8 :: - print pend + print pend + +.. R9 We can see that ``pend`` has all the data of the file. Type just ``pend`` to see more explicitly, what it contains. + +.. L9 :: - pend + pend -Following is an exercise that you must do. +.. L10 -{{ show slide with Question 1 }} +{{{ show slide with Question 1 }}} -%%1%% Split the variable into a list, ``pend_list``, of the lines in -the file. Hint, use the tab command to see what methods the string -variable has. +.. R10 -Please, pause the video here. Do the exercise and then continue. +Pause the video here, try out the following exercise and resume the video. -{{ show slide with Solution 1 }} +Split the variable into a list, ``pend_list``, of the lines in +the file. +.. L11 :: - pend_list = pend.splitlines() + pend_list = pend.splitlines() + pend_list + +.. R11 - pend_list +We use the function ``splitlines`` to solve this problem. + +.. R12 Now, let us learn to read the file line-by-line. But, before that we will have to close the file, since the file has already been read till the end. Let us close the file opened into f. + +.. L12 :: - f.close() + f.close() + +.. R13 -Let us again type ``f`` on the prompt to see what it shows. +Again type ``f`` on the prompt to see what it contains. + +.. L13 :: - f + f + +.. R14 Notice, that it now says the file has been closed. It is a good programming practice to close any file objects that we have opened, after their job is done. -Let us, now move on to reading files line-by-line. +.. L14 + +.. L15 -Following is an exercise that you must do. +{{{ Show slide with Question 2 }}} + +.. R15 + +Let us, now move on to reading files line-by-line. +Pause the video here, try out the following exercise and resume the video. -%%2%% Re-open the file ``pendulum.txt`` with ``f`` as the file object. +Re-open the file ``pendulum.txt`` with ``f`` as the file object. -Please, pause the video here. Do the exercise and then continue. +.. R16 We just use the up arrow until we reach the open command and issue it again. + +.. L16 :: - f = open('/home/fossee/pendulum.txt') + f = open('/home/fossee/pendulum.txt') + +.. R17 Now, to read the file line-by-line, we iterate over the file object line-by-line, using the ``for`` command. Let us iterate over the file line-wise and print each of the lines. + +.. L17 :: - for line in f: - print line + for line in f: + print line + +.. R18 -``line`` is variable, sometimes called the loop +``line`` is a variable, sometimes called the loop variable, and it is not a keyword. We could have used any other variable name, but ``line`` seems meaningful enough. +.. L18 + +.. R19 + Instead of just printing the lines, let us append them to a list, ``line_list``. We first initialize an empty list, ``line_list``. + +.. L19 :: - line_list = [ ] + line_list = [ ] + +.. R20 Let us then read the file line-by-line and then append each of the -lines, to the list. We could, as usual close the file using +lines to the list. We could, as usual close the file using ``f.close`` and re-open it. But, this time, let's leave alone the file object ``f`` and directly open the file within the for statement. This will save us the trouble of closing the file, each time we open it. +.. L20 :: - for line in open('/home/fossee/pendulum.txt'): - line_list.append(line) + for line in open('/home/fossee/pendulum.txt'): + line_list.append(line) + +.. R21 Let us see what ``line_list`` contains. + +.. L21 :: - line_list + line_list + +.. R22 Notice that ``line_list`` is a list of the lines in the file, along with the newline characters. If you noticed, ``pend_list`` did not -contain the newline characters, because the string ``pend`` was +contain the newline characters, because the string ``pend``, was split on the newline characters. -Using some string methods, that we shall look at in the tutorial on -strings, we can strip out the newline characters from the lines. +We can strip out the newline characters from the lines by using some string methods +which we shall look in the further tutorial on strings. + +.. L22 + +.. L23 + +{{{ Show the summary slide }}} -.. #[[Anoop: I think the code that are required to be typed can be - added to the slide.]] +.. R23 -{{{ show the summary slide }}} +This brings us to the end of this tutorial. In this tutorial, we learnt to, + + 1. Open and close files using the ``open`` and ``close`` functions respectively. + #. Read the data in the files as a whole,by using the ``read`` function. + #. Read the data in the files line by line by iterating over the file object using the + ``for`` loop. + #. Append the lines of a file to a list using the ``append`` function within the + ``for`` loop. -That brings us to the end of this tutorial. In this tutorial we -have learnt to open and close files, read the data in the files as -a whole, using the read command or reading it line by line by -iterating over the file object. +.. L24 -{{{ Show the "sponsored by FOSSEE" slide }}} +{{{Show self assessment questions slide}}} -This tutorial was created as a part of FOSSEE project, NME ICT, MHRD India +.. R24 + +Here are some self assessment questions for you to solve + +1. The ``open`` function returns a + + - string + - list + - file object + - function + +2. What does the function ``splitlines()`` do. + + - Displays the data as strings,all in a line + - Displays the data line by line as strings + - Displays the data line by line but not as strings + +.. L25 + +{{{solution of self assessment questions on slide}}} + +.. R25 + +And the answers, + +1. The function ``open``, returns a file object. +2. The function ``splitlines`` displays the data line by line as strings. + +.. L26 + +{{{ Show the Thankyou slide }}} + +.. R26 Hope you have enjoyed and found it useful. Thank you! - |