Python/C2/loading-data-from-files/English-timed

Visual Cue	Narration
0:01	Hello Friends and Welcome to this tutorial on "loading data from files".
0:06	At the end of this tutorial, you will be able to, Read data from files, containing a single column of data Read multiple columns of data, separated by spaces or other delimiters.
0:19	Let us switch to the terminal and start IPython, using ipython hypen pylab
0:33	Now, Let us begin with reading the file primes.txt, which contains a list of prime numbers listed in a column, using the loadtxt command.
0:45	Please make sure that you provide the correct path of the file, 'primes.txt'.
0:50	The file, in our case, is present in slash home slash fossee slash primes.txt.
0:59	Otherwise we can use the cat command to locate the file and read the contents of it.
1:05	So type cat slash home slash fossee slash primes.txt
1:15	Now let us read this list into the variable primes.
1:20	So type primes = loadtxt within bracket in single quotes slash home slash fossee slash primes.txt
1:41	primes is now a sequence of prime numbers, that was listed in the file,``primes.txt``.
1:49	We now type,print space primes to see the sequence printed.
2:00	We observe that all the numbers end with a period.
2:04	This is so, because these numbers are actually read as floats
2:10	Now, let us use the loadtxt command to read a file pendulum.txt that contains two columns of data.
2:19	This file contains the length of the pendulum in the first column and the corresponding time period in the second.
2:26	Note that here loadtxt needs both the columns to have equal number of rows.
2:31	We use the cat command to view the contents of this file.
2:36	So type cat slash home slash fossee slash pendulum.txt
2:50	Let us, now, read the data into the variable pend.
2:55	Again, it is assumed that the file is in slash home slash fossee
3:02	So type pend = loadtxt within bracket in single quote slash home slash fossee slash pendulum.txt
3:21	Let us now print the variable pend and see what it contains.
3:26	So type print pend
3:31	Notice that pend is not a simple sequence like primes .
3:35	It has two sequences, containing both the columns of the data file.
3:40	Let us use an additional argument of the loadtxt command, to read it into two separate, simple sequences.
3:50	So type L, T space = space loadtxt within bracket single quoteslash home slash fossee slash pendulum.txt comma unpack=True
4:23	Let us now, print the variables L and T, to see what they contain.
4:29	So type print space L print space T
4:39	Notice, that L and T now contain the first and second columns of data from the data file, pendulum.txt, and they are both simple sequences.
4:50	unpack=True has given us the two columns into two separate sequences instead of one complex sequence.
5:00	Till now, we have learnt the basic use of the loadtxt command.
5:05	Let us try an example.
5:07	Pause the video here, try out the following exercise and resume the video.
5:12	Read the file pendulum underscore semicolon.txt which contains the same data as pendulum.txt, but the columns are separated by semi-colons instead of spaces.
5:27	Use the IPython help to see how to do this.
5:34	Switch back to the terminal L comma T = loadtxt within bracket in single quote slash home slash fossee slash pendulum underscore semicolon.txt comma unpack=True comma delimiter=semi-colon within single quote
6:54	Okay then type print L
6:40	print T
6:45	This brings us to the end of this tutorial.
6:48	In this tutorial, we have learnt to,
6:51	1. To Read data from files, containing a single column of data using the loadtxt command.
6:58	2. To Read multiple columns of data, separated by spaces or other delimiters.
7:04	Here are some self assessment questions for you to solve 1. loadtxt can read data from a file with one column only. True or False?
7:18	2. Given a file data.txt with three columns of data separated by spaces, read it into 3 separate simple sequences.
7:29	3. Given a file data.txt with three columns of data separated by ":", read it into 3 separate simple sequences.
7:45	And the answers,1. False.
7:50	loadtxt command can read data from files having both single columns as well as multiple columns.
7:58	2. A file with three columns of data separated by spaces to be read into 3 separate sequences, we use the loadtxt command as, x = loadtxt within bracket in double quotes data.txt comma unpack=True
8:19	3. If a file with three columns of data separated by delimiters,we read it into three separate sequences by using an additional argument of delimiter in the loadtxt command x = loadtxt within bracket in double quotes data.txt comma unpack=True comma delimiter=in double quotes colon)
8:51	Hope you have enjoyed this tutorial and found it useful.
8:55	Thank you!

Contributors and Content Editors

Gaurav, Minal, PoojaMoolya, Sneha