Python Diaries Chapter 2

  Divyanshu Bansal  |    June 25, 2018

Link for the first article --> [Python Diaries chapter 1][1] <br> In the previous article I've mentioned the syntax for most basic functions, now I will explain some of them in detailed manner. Also, this article will cover the concepts of string manipulation **Let us start with our beloved PRINT** In the previous post I showed how to **print** in same line and on different lines but only for single variable, let us take one step forward and see how to print multiple variable using only one 'print'. ``` a = 5 b = 'string' print "a is an integer equal to %d and b is a string equal to %s" %(a,b) ``` ``` Output--> a is an integer equal to 5 and b is a string equal to string ``` To print variable inside a print containing text, use format specifiers ie.<br> %d for integer<br> %f for float<br> %s for string<br> To link format specifier to the particular variable, write name of the variable in parenthesis after the closing quotes and appending a percent sign.<br> *Remember to separate variables using commas between variable names.* One more thing, if you wanna print a variable at the end of the text, you can simply do like this ``` print "value of variable a is",a ``` ``` Output-> value of variable a is 5 ``` That's enough of output for now, let's move on to input Suppose you're making an app/software etc. Now you want user to input some data and want to tell user what type of data to be entered **To input string we use** ``` variable = raw_input() ``` just pass the text you want to display to user as argument example ``` variable = raw_input("Enter your age ") ``` ``` Output--> Enter your age #system will wait until user enters some value ``` We are done with I/O for now, let us take a look at some string manipulation functions The classical problem falling under string manipulation category is "**convert text to lower-case/upper-case**". <br> Python has built-in standard methods (no need to import any module) to do this which sometimes haunts a beginner..Right,huh?? here is an example ``` my_string = "stellar" new_string = my_string.upper() print new_string ``` ``` Output --> STELLAR ``` Similarly to convert to lower-case just ***replace 'upper' with 'lower'*** in above code like this--> **new_string=my_string.lower()** But hey look my_string has only first part of my name, where's the rest? Let us make a string which has my full name ``` good_string = "stellar coder" ``` Hmmm, that's okay....but it would have been better if 's' and 'c' were capitalized..<br> Now i will tell you a method which was made to do exactly this task :-) ``` better_string = good_string.title() print better_string ``` ``` Output --> Stellar Coder ``` That looks nice !!!!!!!!! Some of you might be wondering 'What's the difference between a function and a method For now you can say anything which is used like this ***"something.method()"*** ie. functionality name after a period , these things are ***METHODS***<br> and if something is like this --> ***function(something)*** ie. variable/data is passed as an argument then we call them ***FUNCTIONS*** Here's the last one and may be you will use this more than others.<br> swapcase--> It swaps the case of all case-based characters ie. Alphabets present in the string and ignores rest.<br> Example ``` my_gun = "ak47" print my_gun.swapcase() ``` ``` Ouput--> AK47 ``` ``` my_name = "sTELLAR cODER" print my_name.swapcase() ``` ``` Output--> Stellar Coder ``` **Now let's look at a very special tool present in python --> [ : : ] (slicing tool)<br>**<br> It is mostly for slicing the built-in types ie. *list, string* . The basic form of the slicing syntax is somelist[start:end:jump], where start is inclusive and end is exclusive.<br> Note--> ***default value of start is 0 and end is length of list/string and jump is 1***<br> Without any further ado, let me show you some code after all that's the only thing which matters ``` a = ['a','b','c','d','e','f','g','h'] print "first four elements",a[:4] ``` ``` Output --> ['a','b','c','d'] ``` ``` print "last four elements",a[-4:] ``` ``` Output --> ['e','f','g','h'] ``` ``` print "middle two",a[3:-3] ``` ``` Output -> ['d','e'] ``` *Tip--> Try some different values on a sample list for better understanding* That's it for now. Python is a very vast language with a wide range of in-built functionalities. I will introduce you to majority of them by the end of this series and most importantly I'll tell you how to use them efficiently <br><br> **In next article I'll introduce you to for-else loop,filter function,list comprehension,map( we have seen it earlier already).** **Then an article only on function. It will include following**-><br> 1. What is a function 2. Uses of function 3. How to use it 4. Special features in python related to function (like yield) I will be posting next article soon....stay tuned ! [1]: https://www.hackerearth.com/notes/python-diaries-chapter-1/

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