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diff --git a/parsing_data.rst b/parsing_data.rst index 993dec4..9a7f85f 100644 --- a/parsing_data.rst +++ b/parsing_data.rst @@ -1,3 +1,8 @@ +.. Author : Nishanth + Internal Reviewer 1 : + Internal Reviewer 2 : + External Reviewer : + Hello friends and welcome to the tutorial on Parsing Data {{{ Show the slide containing title }}} @@ -6,15 +11,20 @@ Hello friends and welcome to the tutorial on Parsing Data In this tutorial, we shall learn - * What is parsing data + * What we mean by parsing data * the string operations required for parsing data * datatype conversion +#[Puneeth]: Changed a few things, here. + +#[Puneeth]: I don't like the way the term "parsing data" has been used, all +through the script. See if that can be changed. + Lets us have a look at the problem {{{ Show the slide containing problem statement. }}} -There is an input file containing huge no.of records. Each record corresponds +There is an input file containing huge no. of records. Each record corresponds to a student. {{{ show the slide explaining record structure }}} @@ -28,16 +38,22 @@ Our job is to calculate the mean of all the maths marks in the region "B". #[Nishanth]: Please note that I am not telling anything about AA since they do not know about any if/else yet. +#[Puneeth]: Should we talk pass/fail etc? I think we should make the problem + simple and leave out all the columns after total marks. -So what exactly is parsing data? +Now what is parsing data. +From the input file, we can see that the data we have is in the form of +text. Parsing this data is all about reading it and converting it into a form +which can be used for computations -- in our case, sequence of numbers. -Parsing data is all about reading the data and converting it into a form which -can be used for computations. In our case, that is numbers. +#[Puneeth]: should the word tokenizing, be used? Should it be defined before + using it? We can clearly see that the problem involves reading files and tokenizing. -.. #[[Amit:Definition of Tokenizing here.]] +#[Puneeth]: the sentence above seems kinda redundant. + Let us learn about tokenizing strings. Let us define a string first. Type :: @@ -48,11 +64,11 @@ We are now going to split this string on whitespace. line.split() -As you can see, we get a list of strings. Which means, when split is called +As you can see, we get a list of strings. Which means, when ``split`` is called without any arguments, it splits on whitespace. In simple words, all the spaces are treated as one big space. -split also can split on a string of our choice. This is acheived by passing +``split`` also can split on a string of our choice. This is acheived by passing that as an argument. But first lets define a sample record from the file. :: @@ -63,8 +79,8 @@ We can see that the string is split on ';' and we get each field seperately. We can also observe that an empty string appears in the list since there are two semi colons without anything in between. -Hence split splits on whitespace if called without an argument and splits on -the given argument if it is called with an argument. +To recap, ``split`` splits on whitespace if called without an argument and +splits on the given argument if it is called with an argument. {{{ Pause here and try out the following exercises }}} @@ -76,13 +92,13 @@ the given argument if it is called with an argument. We see that when we split on space, multiple whitespaces are not clubbed as one and there is an empty string everytime there are two consecutive spaces. -Now that we know how to split a string, we can split the record and retreive each -field seperately. But there is one problem. The region code "B" and a "B" +Now that we know how to split a string, we can split the record and retrieve +each field seperately. But there is one problem. The region code "B" and a "B" surrounded by whitespace are treated as two different regions. We must find a way to remove all the whitespace around a string so that "B" and a "B" with white spaces are dealt as same. -This is possible by using the =strip= method of strings. Let us define a +This is possible by using the ``strip`` method of strings. Let us define a string by typing :: @@ -110,20 +126,21 @@ By now we know enough to seperate fields from the record and to strip out any white space. The only road block we now have is conversion of string to float. The splitting and stripping operations are done on a string and their result is -also a string, hence the marks that we have are still strings and mathematical -operations on them are not possible. We must convert them into integers or floats +also a string. hence the marks that we have are still strings and mathematical +operations are not possible on them. We must convert them into numbers +(integers or floats), before we can perform mathematical operations on them. -We shall look at converting strings into floats. We define an float string -first. Type +We shall look at converting strings into floats. We define a float string +first. Type :: mark_str = "1.25" - mark = float(mark_str) + mark = int(mark_str) type(mark_str) type(mark) We can see that string is converted to float. We can perform mathematical -operations on it now. +operations on them now. {{{ Pause here and try out the following exercises }}} @@ -131,8 +148,6 @@ operations on it now. {{{ continue from paused state }}} -.. #[[Amit:I think there should be some interaction first here about the -problem before we conclude to talking about the result.]] It raises an error since converting a float string into integer directly is not possible. It involves an intermediate step of converting to float. :: @@ -143,7 +158,7 @@ not possible. It involves an intermediate step of converting to float. number = int(flt) number -Using =int= it is possible to convert float into integers. +Using ``int`` it is also possible to convert float into integers. Now that we have all the machinery required to parse the file, let us solve the problem. We first read the file line by line and parse each record. We see if @@ -162,7 +177,7 @@ the region code is B and store the marks accordingly. if region_code == "AA": math_marks_B.append(math_mark) -.. #[[Amit:This intutively does not seem to be what you wanted]] + Now we have all the maths marks of region "B" in the list math_marks_B. To get the mean, we just have to sum the marks and divide by the length. @@ -179,7 +194,6 @@ we have learnt * how to tokenize a string using various delimiters * how to get rid of extra white space around * how to convert from one type to another -.. #[[Amit:one datatype to another may be better.]] * how to parse input data and perform computations on it {{{ Show the "sponsored by FOSSEE" slide }}} @@ -188,9 +202,5 @@ we have learnt This tutorial was created as a part of FOSSEE project, NME ICT, MHRD India Hope you have enjoyed and found it useful. -Thankyou +Thank you -.. Author : Nishanth - Internal Reviewer 1 : Amit Sethi - Internal Reviewer 2 : - External Reviewer : |