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

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 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. 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.