PoojaMoolya at 06:25, 28 April 2017

2017-04-28T06:25:42Z

PoojaMoolya at 12:04, 20 February 2017

2017-02-20T12:04:46Z

Gaurav at 08:59, 10 July 2014

2014-07-10T08:59:06Z

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Sneha at 07:10, 15 March 2013

2013-03-15T07:10:27Z

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Minal: Created page with '{| border=1 !Timing !Narration |- | 0:00 | Hello Friends and Welcome to the tutorial on "Getting started with files". |- | 0:08 | At the end of this tutorial, you will be able t…'

2013-01-02T10:58:14Z

Created page with '{| border=1 !Timing !Narration |- | 0:00 | Hello Friends and Welcome to the tutorial on "Getting started with files". |- | 0:08 | At the end of this tutorial, you will be able t…'

New page

{| border=1
!Timing
!Narration
|-
| 0:00
| Hello Friends and Welcome to the tutorial on "Getting started with files".

|-
| 0:08
| At the end of this tutorial, you will be able to,

# 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.

|-
| 0:24
| Before beginning this tutorial,we would suggest you to complete the tutorial on "Getting started with Lists" and "Getting started with For".

|-
|0:34
|So now, open the terminal and start ipython

|-
|0:37
|So type ipython space hyphen pylab.

|-
| 0:46
| Let us first open the file, <tt>pendulum dot txt</tt> present in <tt> slash home slash fossee slash</tt>.

|-
|0:54
|So type f is equal to open within brackets and single quotes slash home slash fossee slash pendulum dot txt.

|-
| 1:11
| Here <tt>f</tt> is called a file object.

|-
| 1:14
| Let us type <tt>f</tt> on the terminal to see what it is.

|-
|1:17
|So type f and hit Enter.

|-
| 1:22
| The file object shows the filepath and mode of the file which is open.

|-
|1:27
| 'r' stand for read only mode and 'w' stands for write mode.

|-
|1:32
| As you can see, this file is open in read only mode.

|-
| 1:40
| We shall first learn to read the whole file into a single variable.

|-
|1:47
| We use the <tt>read</tt> method to read all the contents of the file into the variable, <tt>pend</tt>.

|-
|1:53
|So type pend is equal to f dot read closing brackets and hit Enter.

|-
| 2:02
| Now, let us see what <tt>pend</tt> contains, by typing Print space pend

|-
|2:11
| We can see that <tt>pend</tt> has all the data of the file.

|-
|2:15
|Type just <tt>pend</tt> to see more explicitly, what it contains.

|-
| 2:25
| So now, Pause the video here, try out the following exercise and resume the video.

|-
| 2:30
| Split the variable into a list, pend underscore list, of the lines in the file.

|-
| 2:40
| We use the function <tt>splitlines</tt> to solve this problem.

|-
|2:44
|So type pend underscore list is equal to pend dot splitlines closing brackets and hit Enter.

|-
| 3:05
| Now, let us learn to read the file line-by-line.

|-
| 3:11
| But, before that we will have to close the file, since the file has already been read till the end.

|-
|3:19
|Let us close the file opened into f.

|-
|3:24
|Then type f dot close closing brackets and hit Enter.

|-
| 3:29
| Again type <tt>f</tt> on the prompt to see what it contains.

|-
| 3:37
| Notice, that it now says the file has been closed.

|-
| 3:42
| It is a good programming practice to close any file objects that we have opened, after their job is done.

|-
| 3:50
| Let us, now move on to reading files line-by-line.

|-
| 3:54
| Pause the video here, try out the following exercise and resume the video.

|-
|4:00
|Re-open the file <tt>pendulum dot txt</tt> with <tt>f</tt> as the file object.

|-
| 4:05
| We just use the up arrow until we reach the open command and issue it again.Then hit Enter.

|-
| 4:18
| Now, to read the file line-by-line, we iterate over the file object line-by-line, using the <tt>for</tt> command.

|-
|4:27
|Let us iterate over the file line-wise and print each of the lines.

|-
|4:35
|So type in the command for space line space in space f colon , then , print line.

|-
| 4:47
| <tt>line</tt> is a variable, sometimes called the loop variable, and it is not a keyword.

|-
|4:53
|We could have used any other variable name, but <tt>line</tt> seems meaningful enough.

|-
| 5:00
| Instead of just printing the lines, let us append them to a list, <tt>line underscore list</tt>.

|-
|5:07
|We first initialize an empty list, <tt>line underscore list</tt>.

|-
|5:12
|for that type line underscore list is equal to square bracket and hit Enter.

|-
| 5:22
| Let us then read the file line-by-line and then append each of the lines to the list.

|-
|5:30
|We could, as usual close the file using <tt>f.close</tt> and re-open it.

|-
|5:36
|But, this time, let's leave alone the file object <tt>f</tt> and directly open the file within the for statement.

|-
|5:43
| This will save us the trouble of closing the file, each time we open it.

|-
|5:49
|So type for line in open within brackets and single quotes slash home slash fossee slash pendulum dot txt colon

line underscore list dot append within brackets line,Hit Enter.

|-
| 6:22
| Let us see what <tt>line underscore list</tt> contains.

|-
|6:26
|so type line underscore list and hit Enter.

|-
| 6:33
| Notice that <tt>line_list</tt> is a list of the lines in the file, along with the newline characters.

|-
| 6:42
| If you noticed, <tt>pend underscore list</tt> did not contain the newline characters, because the string <tt>pend</tt>, was split on the newline characters.

|-
|6:52
|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.

|-
|7:04
| So now, This brings us to the end of this tutorial. Lets revise what we have learnt,

|-
|7:12
|1. Open and close files using the <tt>open</tt> and <tt>close</tt> functions respectively.

|-
|7:17
|2. Read the data in the files as a whole,by using the <tt>read</tt> function.

|-
|7:22
|3. Read the data in the files line by line by iterating over the file object using the <tt>for</tt> loop.

|-
|7:31
|and finally Append the lines of a file to a list using the <tt>append</tt> function within the <tt>for</tt> loop.

|-
| 7:38
| Here are some self assessment questions for you to solve

|-
|7:42
|1. The <tt>open</tt> function returns a

|-
|7:46
| string

|-
|7:48
| list

|-
|7:49
| file object

|-
|7:50
| function

|-
|7:52
|2. What does the function <tt>splitlines()</tt> do.

|-
|7:57
| Displays the data as strings,all in a line

|-
|8:01
| Displays the data line by line as strings

|-
|8:03
| Displays the data line by line but not as strings

|-
| 8:07
| So now,let us look at the answers,

|-
|8:09
|1.The function <tt>open</tt>, returns a file object.

|-
|8:15
|2. The function <tt>splitlines</tt> displays the data line by line as strings.

|-
| 8:21
| So we hope you have enjoyed this tutorial and found it useful.

|-
|8:27
|Thank you!

|}

@@ Line 251: / Line 251: @@
 |-
 |07:48
-| list
+| list,file object
-−
-|-
-|07:49
-| file object
 |-

@@ Line 10: / Line 10: @@
 | 00:08
 | At the end of this tutorial, you will be able to,
 Open a file.
-# Open a file.
+Read the contents of the file line by line.
-# Read the contents of the file line by line.
+Read the entire content of file at once.
-# Read the entire content of file at once.
+Append the lines of a file to a list.
-# Append the lines of a file to a list.
+Close the file.
-# Close the file.
 |-
@@ Line 196: / Line 195: @@
 |05:49
 |So type for line in open within brackets and single quotes slash home slash fossee slash pendulum dot txt colon
 line underscore list dot append within brackets line,Hit Enter.
-    line underscore list dot append within brackets line,Hit Enter.
 |-
@@ Line 225: / Line 223: @@
 |-
 |07:12
-|1. Open and close files using the  open  and  close  functions respectively.
+|Open and close files using the  open  and  close  functions respectively.
 |-
 |07:17
-|2. Read the data in the files as a whole,by using the read  function.
+|Read the data in the files as a whole,by using the read  function.
 |-
 |07:22
-|3. Read the data in the files line by line by iterating over the file object using the  for  loop.
+|Read the data in the files line by line by iterating over the file object using the  for  loop.
 |-
@@ Line 245: / Line 243: @@
 |-
 |07:42
-|1. The open  function returns a
+|The open  function returns a
 |-
@@ Line 265: / Line 263: @@
 |-
 |07:52
-|2. What does the function  splitlines()  do.
+|What does the function  splitlines()  do.
 |-
@@ Line 285: / Line 283: @@
 |-
 |08:09
-|1.The function  open , returns a file object.
+|The function  open , returns a file object.
 |-
 |08:15
-|2. The function  splitlines  displays the data line by line as strings.
+|The function  splitlines  displays the data line by line as strings.
 |-

Python/C3/Getting-started-with-files/English-timed - Revision history

PoojaMoolya at 06:25, 28 April 2017

PoojaMoolya at 12:04, 20 February 2017

Gaurav at 08:59, 10 July 2014

Sneha at 07:10, 15 March 2013

Minal: Created page with '{| border=1 !Timing !Narration |- | 0:00 | Hello Friends and Welcome to the tutorial on "Getting started with files". |- | 0:08 | At the end of this tutorial, you will be able t…'