Difference between revisions of "Python/C3/Getting-started-with-files/English-timed"

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{| border=1
 
{| border=1
−
!Timing
+
|'''Time'''
−
!Narration
+
|'''Narration'''
 +
 
 
|-
 
|-
−
| 0:00
+
|00:00
 
| Hello Friends and Welcome to the tutorial on "Getting started with files".
 
| Hello Friends and Welcome to the tutorial on "Getting started with files".
  
 
|-
 
|-
−
| 0:08
+
| 00:08
 
| At the end of this tutorial, you will be able to,
 
| 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.
+
  
 
|-
 
|-
−
| 0:24
+
| 00:24
 
| Before beginning this tutorial,we would suggest you to complete the tutorial on "Getting started with Lists" and "Getting started with For".
 
| Before beginning this tutorial,we would suggest you to complete the tutorial on "Getting started with Lists" and "Getting started with For".
  
 
|-
 
|-
−
|0:34
+
|00:34
 
|So now, open the terminal and start ipython
 
|So now, open the terminal and start ipython
  
 
|-
 
|-
−
|0:37
+
|00:37
 
|So type ipython space hyphen pylab.
 
|So type ipython space hyphen pylab.
  
 
|-
 
|-
−
|  0:46
+
|  00:46
−
| Let us first open the file, <tt>pendulum dot txt</tt> present in <tt> slash home slash fossee slash</tt>.
+
| Let us first open the file, pendulum dot txt present in slash home slash fossee slash .
  
 
|-
 
|-
−
|0:54
+
|00:54
 
|So type f is equal to open within brackets and single quotes slash home slash fossee slash pendulum dot txt.  
 
|So type f is equal to open within brackets and single quotes slash home slash fossee slash pendulum dot txt.  
  
 
|-
 
|-
−
|  1:11
+
|  01:11
−
| Here <tt>f</tt> is called a file object.
+
| Here f is called a file object.
  
 
|-
 
|-
−
| 1:14
+
| 01:14
−
| Let us type <tt>f</tt> on the terminal to see what it is.
+
| Let us type f on the terminal to see what it is.
  
 
|-
 
|-
−
|1:17
+
|01:17
 
|So type f and hit Enter.
 
|So type f and hit Enter.
  
 
|-
 
|-
−
| 1:22
+
| 01:22
 
| The file object shows the filepath and mode of the file which is open.
 
| The file object shows the filepath and mode of the file which is open.
  
 
|-
 
|-
−
|1:27
+
|01:27
 
| 'r' stand for read only mode and 'w' stands for write mode.
 
| 'r' stand for read only mode and 'w' stands for write mode.
  
 
|-
 
|-
−
|1:32
+
|01:32
 
| As you can see, this file is open in read only mode.
 
| As you can see, this file is open in read only mode.
  
 
|-
 
|-
−
| 1:40
+
| 01:40
 
| We shall first learn to read the whole file into a single variable.
 
| We shall first learn to read the whole file into a single variable.
  
 
|-
 
|-
−
|1:47
+
|01:47
−
| We use the <tt>read</tt> method to read all the contents of the file into the variable, <tt>pend</tt>.
+
| We use the read method to read all the contents of the file into the variable,pend.
  
 
|-
 
|-
−
|1:53
+
|01:53
 
|So type pend is equal to f dot read closing brackets and hit Enter.  
 
|So type pend is equal to f dot read closing brackets and hit Enter.  
  
 
|-
 
|-
−
|  2:02
+
|  02:02
−
| Now, let us see what <tt>pend</tt> contains, by typing Print space pend
+
| Now, let us see what pend contains, by typing Print space pend
  
 
|-
 
|-
−
|2:11
+
|02:11
−
| We can see that <tt>pend</tt> has all the data of the file.  
+
| We can see that pend has all the data of the file.  
  
 
|-
 
|-
−
|2:15
+
|02:15
−
|Type just <tt>pend</tt> to see more explicitly, what it contains.
+
|Type just pend to see more explicitly, what it contains.
  
 
|-
 
|-
−
| 2:25
+
| 02:25
 
| So now, Pause the video here, try out the following exercise and resume the video.
 
| So now, Pause the video here, try out the following exercise and resume the video.
  
 
|-
 
|-
−
| 2:30
+
| 02:30
 
| Split the variable into a list, pend underscore list, of the lines in the file.
 
| Split the variable into a list, pend underscore list, of the lines in the file.
  
 
|-
 
|-
−
|  2:40
+
|  02:40
−
| We use the function <tt>splitlines</tt> to solve this problem.
+
| We use the function split lines to solve this problem.
  
 
|-
 
|-
−
|2:44
+
|02:44
−
|So type pend underscore list is equal to pend dot splitlines closing brackets and hit Enter.
+
|So type pend underscore list is equal to pend dot split lines closing brackets and hit Enter.
  
 
|-
 
|-
−
|  3:05
+
|  03:05
 
| Now, let us learn to read the file line-by-line.
 
| Now, let us learn to read the file line-by-line.
  
 
|-
 
|-
−
| 3:11
+
| 03:11
 
| But, before that we will have to close the file, since the file has already been read till the end.
 
| But, before that we will have to close the file, since the file has already been read till the end.
  
 
|-
 
|-
−
|3:19
+
|03:19
 
|Let us close the file opened into f.
 
|Let us close the file opened into f.
  
 
|-
 
|-
−
|3:24
+
|03:24
 
|Then type f dot close closing brackets and hit Enter.
 
|Then type f dot close closing brackets and hit Enter.
  
 
|-
 
|-
−
|  3:29
+
|  03:29
−
| Again type <tt>f</tt> on the prompt to see what it contains.
+
| Again type f   on the prompt to see what it contains.
  
 
|-
 
|-
−
| 3:37
+
| 03:37
 
| Notice, that it now says the file has been closed.
 
| Notice, that it now says the file has been closed.
  
 
|-
 
|-
−
| 3:42
+
| 03:42
 
| It is a good programming practice to close any file objects that we have opened, after their job is done.
 
| It is a good programming practice to close any file objects that we have opened, after their job is done.
  
 
|-
 
|-
−
| 3:50
+
| 03:50
 
| Let us, now move on to reading files line-by-line.
 
| Let us, now move on to reading files line-by-line.
  
 
|-
 
|-
−
| 3:54
+
| 03:54
 
| Pause the video here, try out the following exercise and resume the video.
 
| Pause the video here, try out the following exercise and resume the video.
  
 
|-
 
|-
−
|4:00
+
|04:00
−
|Re-open the file <tt>pendulum dot txt</tt> with <tt>f</tt> as the file object.
+
|Re-open the file pendulum dot txt with f as the file object.
  
 
|-
 
|-
−
|  4:05
+
|  04:05
 
| We just use the up arrow until we reach the open command and issue it again.Then hit Enter.
 
| We just use the up arrow until we reach the open command and issue it again.Then hit Enter.
  
 
|-
 
|-
−
|  4:18
+
|  04:18
−
| Now, to read the file line-by-line, we iterate over the file object line-by-line, using the <tt>for</tt> command.  
+
| Now, to read the file line-by-line, we iterate over the file object line-by-line, using the for command.  
  
 
|-
 
|-
−
|4:27
+
|04:27
 
|Let us iterate over the file line-wise and print each of the lines.
 
|Let us iterate over the file line-wise and print each of the lines.
  
 
|-
 
|-
−
|4:35
+
|04:35
 
|So type in the command for space line space in space f colon , then , print line.
 
|So type in the command for space line space in space f colon , then , print line.
  
 
|-
 
|-
−
| 4:47
+
| 04:47
−
| <tt>line</tt> is a variable, sometimes called the loop variable, and it is not a keyword.  
+
|line is a variable, sometimes called the loop variable, and it is not a keyword.  
  
 
|-
 
|-
−
|4:53
+
|04:53
−
|We could have used any other variable name, but <tt>line</tt> seems meaningful enough.
+
|We could have used any other variable name, but line seems meaningful enough.
  
 
|-
 
|-
−
| 5:00
+
| 05:00
−
| Instead of just printing the lines, let us append them to a list, <tt>line underscore list</tt>.  
+
| Instead of just printing the lines, let us append them to a list, line underscore list .  
−
 
+
−
 
+
  
 
|-
 
|-
−
|5:07
+
|05:07
−
|We first initialize an empty list, <tt>line underscore list</tt>.
+
|We first initialize an empty list, line underscore list.
  
 
|-
 
|-
−
|5:12
+
|05:12
 
|for that type line underscore list is equal to square bracket and hit Enter.
 
|for that type line underscore list is equal to square bracket and hit Enter.
  
 
|-
 
|-
−
|  5:22
+
|  05:22
 
| Let us then read the file line-by-line and then append each of the lines to the list.  
 
| Let us then read the file line-by-line and then append each of the lines to the list.  
  
 
|-
 
|-
−
|5:30
+
|05:30
−
|We could, as usual close the file using <tt>f.close</tt> and re-open it.  
+
|We could, as usual close the file using f.close and re-open it.  
  
 
|-
 
|-
−
|5:36
+
|05:36
−
|But, this time, let's leave alone the file object <tt>f</tt> and directly open the file within the for statement.
+
|But, this time, let's leave alone the file object f and directly open the file within the for statement.
  
 
|-
 
|-
−
|5:43
+
|05:43
 
| This will save us the trouble of closing the file, each time we open it.
 
| This will save us the trouble of closing the file, each time we open it.
  
 
|-
 
|-
−
|5:49
+
|05:49
 
|So type for line in open within brackets and single quotes slash home slash fossee slash pendulum dot txt colon
 
|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.
+
−
 
+
  
 
|-
 
|-
−
|  6:22
+
|  06:22
−
| Let us see what <tt>line underscore list</tt> contains.
+
| Let us see what line underscore list contains.
  
 
|-
 
|-
−
|6:26
+
|06:26
 
|so type line underscore list and hit Enter.
 
|so type line underscore list and hit Enter.
  
 
|-
 
|-
−
| 6:33
+
| 06:33
−
| Notice that <tt>line_list</tt> is a list of the lines in the file, along with the newline characters.
+
| Notice that line_list is a list of the lines in the file, along with the newline characters.
  
 
|-
 
|-
−
| 6:42
+
| 06:42
−
| 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.
+
| If you noticed, pend underscore list did not contain the newline characters, because the string pend was split on the newline characters.
  
 
|-
 
|-
−
|6:52
+
|06:52
 
|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.
 
|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
+
|07:04
 
| So now, This brings us to the end of this tutorial. Lets revise what we have learnt,
 
| So now, This brings us to the end of this tutorial. Lets revise what we have learnt,
  
 
|-
 
|-
−
|7:12
+
|07:12
−
|1. Open and close files using the <tt>open</tt> and <tt>close</tt> functions respectively.
+
|Open and close files using the open and close functions respectively.
  
 
|-
 
|-
−
|7:17
+
|07:17
−
|2. Read the data in the files as a whole,by using the <tt>read</tt> function.
+
|Read the data in the files as a whole,by using the read function.
  
 
|-
 
|-
−
|7:22
+
|07:22
−
|3. Read the data in the files line by line by iterating over the file object using the <tt>for</tt> loop.
+
|Read the data in the files line by line by iterating over the file object using the for loop.
  
 
|-
 
|-
−
|7:31
+
|07:31
−
|and finally Append the lines of a file to a list using the <tt>append</tt> function within the <tt>for</tt> loop.
+
|and finally Append the lines of a file to a list using the append function within the for loop.
  
 
|-
 
|-
−
| 7:38
+
| 07:38
−
| Here are some self assessment questions for you to solve
+
| Here are some self assessment questions for you  
  
 
|-
 
|-
−
|7:42
+
|07:42
−
|1. The <tt>open</tt> function returns a
+
|The open function returns a
  
 
|-
 
|-
−
|7:46
+
|07:46
 
| string
 
| string
  
 
|-
 
|-
−
|7:48
+
|07:48
−
| list
+
| list,file object
  
 
|-
 
|-
−
|7:49
+
|07:50
−
| file object
+
−
 
+
−
|-
+
−
|7:50
+
 
| function
 
| function
  
 
|-
 
|-
−
|7:52
+
|07:52
−
|2. What does the function <tt>splitlines()</tt> do.
+
|What does the function splitlines() do.
  
 
|-
 
|-
−
|7:57
+
|07:57
 
| Displays the data as strings,all in a line
 
| Displays the data as strings,all in a line
  
 
|-
 
|-
−
|8:01
+
|08:01
 
| Displays the data line by line as strings
 
| Displays the data line by line as strings
  
 
|-
 
|-
−
|8:03
+
|08:03
 
| Displays the data line by line but not as strings
 
| Displays the data line by line but not as strings
  
 
|-
 
|-
−
| 8:07
+
| 08:07
 
| So now,let us look at the answers,
 
| So now,let us look at the answers,
  
 
|-
 
|-
−
|8:09
+
|08:09
−
|1.The function <tt>open</tt>, returns a file object.
+
|The function open , returns a file object.
  
 
|-
 
|-
−
|8:15
+
|08:15
−
|2. The function <tt>splitlines</tt> displays the data line by line as strings.
+
|The function splitlines displays the data line by line as strings.
−
 
+
−
 
+
  
 
|-
 
|-
−
| 8:21
+
| 08:21
 
| So we hope you have enjoyed this tutorial and found it useful.  
 
| So we hope you have enjoyed this tutorial and found it useful.  
  
 
|-
 
|-
−
|8:27
+
|08:27
 
|Thank you!
 
|Thank you!
  
 
|}
 
|}

Latest revision as of 11:55, 28 April 2017

Time Narration
00:00 Hello Friends and Welcome to the tutorial on "Getting started with files".
00:08 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.

00:24 Before beginning this tutorial,we would suggest you to complete the tutorial on "Getting started with Lists" and "Getting started with For".
00:34 So now, open the terminal and start ipython
00:37 So type ipython space hyphen pylab.
00:46 Let us first open the file, pendulum dot txt present in slash home slash fossee slash .
00:54 So type f is equal to open within brackets and single quotes slash home slash fossee slash pendulum dot txt.
01:11 Here f is called a file object.
01:14 Let us type f on the terminal to see what it is.
01:17 So type f and hit Enter.
01:22 The file object shows the filepath and mode of the file which is open.
01:27 'r' stand for read only mode and 'w' stands for write mode.
01:32 As you can see, this file is open in read only mode.
01:40 We shall first learn to read the whole file into a single variable.
01:47 We use the read method to read all the contents of the file into the variable,pend.
01:53 So type pend is equal to f dot read closing brackets and hit Enter.
02:02 Now, let us see what pend contains, by typing Print space pend
02:11 We can see that pend has all the data of the file.
02:15 Type just pend to see more explicitly, what it contains.
02:25 So now, Pause the video here, try out the following exercise and resume the video.
02:30 Split the variable into a list, pend underscore list, of the lines in the file.
02:40 We use the function split lines to solve this problem.
02:44 So type pend underscore list is equal to pend dot split lines closing brackets and hit Enter.
03:05 Now, let us learn to read the file line-by-line.
03:11 But, before that we will have to close the file, since the file has already been read till the end.
03:19 Let us close the file opened into f.
03:24 Then type f dot close closing brackets and hit Enter.
03:29 Again type f on the prompt to see what it contains.
03:37 Notice, that it now says the file has been closed.
03:42 It is a good programming practice to close any file objects that we have opened, after their job is done.
03:50 Let us, now move on to reading files line-by-line.
03:54 Pause the video here, try out the following exercise and resume the video.
04:00 Re-open the file pendulum dot txt with f as the file object.
04:05 We just use the up arrow until we reach the open command and issue it again.Then hit Enter.
04:18 Now, to read the file line-by-line, we iterate over the file object line-by-line, using the for command.
04:27 Let us iterate over the file line-wise and print each of the lines.
04:35 So type in the command for space line space in space f colon , then , print line.
04:47 line is a variable, sometimes called the loop variable, and it is not a keyword.
04:53 We could have used any other variable name, but line seems meaningful enough.
05:00 Instead of just printing the lines, let us append them to a list, line underscore list .
05:07 We first initialize an empty list, line underscore list.
05:12 for that type line underscore list is equal to square bracket and hit Enter.
05:22 Let us then read the file line-by-line and then append each of the lines to the list.
05:30 We could, as usual close the file using f.close and re-open it.
05:36 But, this time, let's leave alone the file object f and directly open the file within the for statement.
05:43 This will save us the trouble of closing the file, each time we open it.
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.

06:22 Let us see what line underscore list contains.
06:26 so type line underscore list and hit Enter.
06:33 Notice that line_list is a list of the lines in the file, along with the newline characters.
06:42 If you noticed, pend underscore list did not contain the newline characters, because the string pend was split on the newline characters.
06:52 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.
07:04 So now, This brings us to the end of this tutorial. Lets revise what we have learnt,
07:12 Open and close files using the open and close functions respectively.
07:17 Read the data in the files as a whole,by using the read function.
07:22 Read the data in the files line by line by iterating over the file object using the for loop.
07:31 and finally Append the lines of a file to a list using the append function within the for loop.
07:38 Here are some self assessment questions for you
07:42 The open function returns a
07:46 string
07:48 list,file object
07:50 function
07:52 What does the function splitlines() do.
07:57 Displays the data as strings,all in a line
08:01 Displays the data line by line as strings
08:03 Displays the data line by line but not as strings
08:07 So now,let us look at the answers,
08:09 The function open , returns a file object.
08:15 The function splitlines displays the data line by line as strings.
08:21 So we hope you have enjoyed this tutorial and found it useful.
08:27 Thank you!

Contributors and Content Editors

Gaurav, Minal, PoojaMoolya, Sneha

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