Difference between revisions of "Python-3.4.3/C2/Loading-Data-From-Files/English-timed"

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| So, type: '' '''''primes'''''(equal to)'''''loadtxt'''''(within parentheses)(within double quotes)'''''primes'''''(dot)'''''txt''''' and press '''Enter.'''
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| So, type: '''primes'''''(equal to)'''''loadtxt'''''(within parentheses)(within double quotes)'''''primes'''''(dot)'''''txt''' and press '''Enter.'''
  
 
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|Now, type: '''cat'''''(space)'''''pendulum'''''(dot)'''''txt ''' and Press '''Enter'''.
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|Now, type: '''cat'''''(space)'''''pendulum'''''(dot)'''''txt ''' and press '''Enter'''.
  
 
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| So, type: '''pend'''''(equal to)'''''loadtxt'''''(within parentheses)(within double quotes)'''''pendulum'''''(dot)'''''txt''''' ''and'' press''' Enter.'''''
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| So, type: '''pend'''''(equal to)'''''loadtxt'''''(within parentheses)(within double quotes)'''''pendulum'''''(dot)'''''txt''''' ''and press''' Enter.'''
  
 
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| Now'' '''''print'''''(within parentheses)'''''L''' and press '''Enter.'''
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| Now, '''print'''''(within parentheses)'''''L''' and press '''Enter.'''
  
'''print'''''(within parentheses)'''''T '''''and press'' '''Enter. '''
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'''print'''''(within parentheses)'''''T ''' and press '''Enter. '''
  
 
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Latest revision as of 11:13, 14 June 2019

Time Narration
00:01 Hello friends and welcome to the spoken tutorial on "loading data from files".
00:07 In this tutorial, you will learn to:

read data from files which contain data in:

single column format

or multiple columns separated by spaces or other delimiters.

00:21 To record this tutorial, I am using:

Ubuntu Linux 14.04 operating system,

Python 3.4.3,

IPython 5.1.0.

00:37 You should know how to run basic Python commands on the ipython console.
00:43 If not, for relevant Python tutorials, please visit this website.

http://spoken-tutorial.org

00:49 Let us first open the Terminal by pressing Ctrl+Alt+T keys simultaneously. Now, type ipython3 and press Enter.
01:02 Let us initialise the pylab package.

Type percent pylab and press Enter.

01:12 Let us begin with reading the file primes.txt. This file contains a list of prime numbers listed in a column.
01:22 Type: cat(space)primes(dot)txt
01:29 We can use the cat command to fetch data from the file and display it on the terminal. Press Enter.
01:38 We see the prime numbers are displayed on the terminal.
01:43 Now we can use the loadtxt() command to store this list into the variable primes.
01:50 So, type: primes(equal to)loadtxt(within parentheses)(within double quotes)primes(dot)txt and press Enter.
02:07 Please make sure that you provide the correct path to the file, 'primes.txt'.
02:13 The file, in our case, is present in the home folder.
02:18 primes is now a sequence of prime numbers that was listed in the file primes.txt.
02:25 Now let us display the contents in the variable primes.
02:29 So, type: print (within parentheses) primes and press Enter. We see the sequence printed.
02:41 We observe that all the numbers end with a period ‘.’ . This is because all these numbers are floats.
02:51 Now, type: cat(space)pendulum(dot)txt and press Enter.
03:01 This file contains two columns of data. This first column contains the length of the pendulum.

The second column contains the corresponding time period.

03:15 Let us now read the data from the file into the variable pend using the loadtxt command.
03:23 So, type: pend(equal to)loadtxt(within parentheses)(within double quotes)pendulum(dot)txt and press Enter.
03:39 Please note that loadtxt needs both the columns of the file to have equal number of rows.
03:47 Now, print the variable pend to see what it contains.

Type: print(within parentheses)pend and press Enter.

04:00 Notice that the variable has two sequences containing two columns of the data file.
04:07 Let us use an additional argument of the loadtxt command to read the data into two separate sequences.
04:16 So, type L(comma)T(equal to)loadtxt(within parentheses within double quotes)pendulum(dot)txt(after double quotes comma)unpack(equal to)True

and press Enter.

04:42 Now print the variables L and T to see what they contain.
04:47 Type: print(within parentheses)L and press Enter.

Type: print(within parentheses)T and press Enter.

05:01 Notice, that L and T now contain the first and second columns of data from the pendulum.txt respectively.
05:12 unpack(equal to)True has made the two columns into two separate and simple sequences.
05:20 Pause the video over here and try out the following exercise and resume the video.
05:27 Read the data from the file pendulum(underscore)semicolon(dot)txt.
05:33 This file contains data in two columns. These columns are separated by semicolons.

Use the IPython help to see how to do this.

05:45 Let us look at the solution. Switch to the terminal.
05:50 First we will see the content of the file.
05:54 So, type: cat space pendulum(underscore)semicolon(dot)txt and press Enter. We see the two columns separated by a semicolon.
06:12 Now, type: L(comma)T(equal to)loadtxt (within parentheses within double quotes) pendulum(underscore)semicolon (dot)txt(after double quotes comma)unpack(equal to)True(comma)delimiter(equal to)(within double quotes)semicolon.

And press Enter.

06:48 Now, print(within parentheses)L and press Enter.

print(within parentheses)T and press Enter.

07:03 This will display the contents inside the two variables L and T.
07:09 This brings us to the end of this tutorial. In this tutorial, we have learnt to read data from files using the loadtxt() command.
07:20 The data can be in:

a single column format or multiple column format, separated by spaces or other delimiters.

07:31 Here are some self assessment questions for you to solve.

1. loadtxt can read data only from a file with one column. Is it True or False?

2. Given a file data.txt with three columns of data separated by spaces. Read it into 3 separate simple sequences.

07:58 3. Given a file data.txt with three columns of data separated by colon. Read it into 3 separate simple sequences.
08:09 Now, let us look at the answers. The answer to the first question is False.
08:17 The loadtxt() command can read data from files having single columns as well as multiple columns.
08:25 The answer to the second question is-

To separate data into three columns, we use the loadtxt() command as follows:

08:35 x(equal to)loadtxt(within parentheses and within double quotes)data(dot)txt(after double quotes comma)unpack(equal to)True.
08:50 The answer to the third question is-

We read into three separate sequences by using an additional argument of delimiter in the loadtxt command.

09:03 So, x(equal to)loadtxt( within parentheses, within double quotes)data(dot)txt(after double quotes comma)unpack(equal to)True(comma)delimiter(equal to)(within double quotes)colon.
09:22 Do you have questions on THIS Spoken Tutorial?. Please visit this site.
09:29 Do you have any general / technical questions? Please visit the forum given in the link.
09:37 The FOSSEE team coordinates coding of solved examples of popular books.
09:43 We give honorarium and certificates for those who do this. For more details, please visit this site.
09:52 The Spoken Tutorial project is funded by NMEICT, MHRD, Govt. of India.
09:59 This is Prathamesh Salunke from IIT Bombay, signing off. Thanks for watching.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14