Python-3.4.3/C2/Parsing-data/English
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Welcome to the spoken tutorial on Parsing-data. |
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Objectives
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In this tutorial, we will learn to-
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System Specifications |
To record this tutorial, I am using
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Prerequisite slide |
To practice this tutorial, you should know how to use lists.
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Parsing Data
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First, let us understand, what is meant by parsing data.
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split() function
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Next we will learn about split() function.
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split() function |
The split function parses a string and returns an array of tokens.
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Press Ctrl+Alt+T keys | Let us first open the terminal by pressing Ctrl+Alt+T keys simultaneously. |
Type ipython3 | Type, ipython3 and press Enter. |
%pylab and press Enter. | Let us initialize the pylab package.
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str1 = "Welcome to Python tutorials"
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From here onwards, please remember to press the Enter key after typing every command on the terminal.
Let us define a variable str1 as string data type.
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str1.split()
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Now, we are going to split this string on whitespace.
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Type
x = "08-26-2009;08-27-2009;08-29-2009"
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Let us take another example for split() function with argument.
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Type x.split(';') | Type, x dot split inside parentheses inside single quotes semicolon. |
Point to the output | We get a list of strings separated by comma. |
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Pause the video.
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Switch to the terminal | Switch to the terminal for the solution. |
Type, b = x.split() | Type, b is equal to x dot split open and close parentheses.
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Type, c = x.split(' ') | Type, c is equal to x dot split open and close parentheses and inside single quotes space. |
Type, b | Type, b |
Type, c | Type, c |
Highlight the output | We can see that splitting without argument is same as giving space as argument. |
Show slide: | Splitting the string without argument will split the string separated by any number of spaces.
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Type str1 | Let us recall the variable str1. |
Type b= str1.split() | Now, we will split this string without argument.
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Type c=str1.split(' ') | Type, c is equal to str1 dot split open and close parentheses and inside single quotes space. |
Type b | Type, b |
Type c | Type, c |
Highlight the output | As you can see, here b is not equal to c since c has whitespaces as entries whereas b has only words.
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strip() function |
Next we will learn about strip method.
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Type unstripped = " Hello world " | Let us define a string by typing
unstripped is equal to inside double quotes space Hello world space |
Type unstripped.strip() | Now to remove the whitespace,
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Highlight output | We can see that strip removes all the white spaces in the beginning and at the end of the string.
After splitting and stripping we get a list of strings with leading and trailing spaces stripped off. <<PAUSE>> |
Type mark_str = "1.25" | Now we shall look at converting strings into floats and integers.
Type, mark underscore str is equal to inside double quotes 1.25
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Type mark = float(mark_str)
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Type, mark is equal to float inside parentheses mark underscore str
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Type type(mark_str) | Type, type inside parentheses mark underscore str
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Type type(mark) | Type, type inside parentheses mark
This shows mark is a float datatype. |
Highlight the output | We can see that string is converted to float.
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Exercise 2
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Pause the video. Try this exercise and then resume the video.
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Switch to terminal | Switch to the terminal for the solution. |
Type int("1.25")
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Type, int inside parentheses inside double quotes 1.25
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Type dcml_str = "1.25" | Let us see the correct solution for this.
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Type flt = float(dcml_str) | Type, flt is equal to float inside parentheses dcml underscore str.
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Type flt | Type, flt |
Type number = int(flt) | Type, number is equal to int inside parentheses flt
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Type number
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Type, number
we got the output as integer. This is how we should convert strings into floats and integers. <<PAUSE>> |
Open the file text editor.
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Next, we will use a data file to parse the data.
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Show text: student_record.txt is available in the Code files link.
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A file student underscore record.txt is available in the Code files link of this tutorial.
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Scroll down and show the records
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We will first read the file line by line and parse each record in this file.
It contains records of students and their marks in the State Secondary Board Examination.
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Highlight A;015163;JOSEPH RAJ S;083;042;47;00;72;244
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Each line in the file is a set of fields separated by semicolons.
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Open text editor | Open a new text editor. |
Copy paste the code from text editor | Type the code as shown. |
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for line in open("student_record.txt"): fields = line.split(";") |
Let me explain this program.
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math_mark = float(math_mark_str)
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The math marks are then converted to float. |
Highlight the code for this narration.
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Then it is appended and stored as a list in a variable math underscore marks underscore A for region code A. |
Save python file as marks.py | Save the file as marks.py in the home directory. |
Switch to terminal | Switch to the terminal. |
Type, %run marks.py | Execute the file with percentage sign run space marks.py. |
Switch to editor
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Switch back to the editor.
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Add in the marks.py file
math_marks_mean = sum(math_marks_A) / len(math_marks_A)
Highlight len(math_marks_A) |
Add the below lines to calculate the mean of math marks for region A.
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Press ctrl + s | Let us save the file. |
Switch to terminal | Switch to the terminal. |
Type, %run marks.py | Execute the file again with percentage sign run space marks.py. |
Highlight output | Hence we get our final output.
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Summary slide
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This brings us to the end of this tutorial.
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Summary slide |
# Remove whitespaces using the strip() function.
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Evaluation
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Here are some self assessment questions for you to solve
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Evaluation |
2. What does int("20.0") produce |
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And the answers,
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Forum |
Please post your timed queries in this forum. |
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Fossee Forum |
Please post your general queries on Python in this forum. |
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Textbook Companion |
FOSSEE team coordinates the TBC project. |
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Acknowledgment |
Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.
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Thank You |
This is Priya from IIT Bombay signing off.
Thanks for watching. |