4. Strings [Python 3 Programming Tutorials]

Key Takeaways

today's topic is strings in Python strings are used to store text data in Python let me show you example so let's say you want to store ice-cream and to do that you create a variable called text and using double quotation mark you type in icecream when you hit Enter what happened is this variable now contains this data called ice cream since you see on the right-hand side here in the picture the way Python stores ice cream is it's a sequence of characters so text starts at specific memory address and then after it's a sequence of characters stored in different memory addresses now using an index you can access in usual characters so for example if I want to access first character I in this variable then the way I do it is using square bracket type in text square bracket 0 if I do that I will get I so if I want to access now see you will do one so each of these initial letters are stored at specific memory locations which can be accessed using these indexes ok if now you want to let's change the content of particular character you would think what if I do this hmm it gives the error so this means strings are immutable once you create them you can change it you can place another string into this variable but you cannot partially change it using the index character so just remember that strings are immutable in Python programming languages other programming languages such as C++ Java they will allow you to do it but not Python now what if I want to access substring within this main string so let's say I want to print ice the way you do it is using the index sub range so I starts at 0 index and E and at 2 but the way sub index works is you have to give index after it so e answer to so Q 3 and when you do it you will get ice here so always remember the first index is included whereas the second one is excluded so whatever is the second index minus one that's then Dax up to which it will go and print your substring similarly if you want to print cream what you'll do is you will first figure out the index of it so it will be zero one two three four and then you will go all of it until the end so five six seven eight nine so you're getting one more here but what if you don't want to supply this index and you just want to say okay start from four and go until the end in that case you can just omit that index so just don't specify the index and it will assume that you want to go all the way towards the end similarly if you omit the index the starting index then it will start from zero so if I do this again I got iced so if you don't specify anything it will assume it's zero you can use double quotes and single quotes to store the text data so for example I can say hello like this so this is defining a string using double quotes or I can use single quote or doing the same thing they both are same thing there's just no difference this could be useful especially if you have single or double quote as part of your string itself for example if I have a string called let's learn Python so let's I will say let's long Python if I do something like this where I used single quotation to as a boundary of my string and I have a quote within my string itself if I do it it will give an error why because it is thinking that this is the end of the string whereas my intention is to make this whole thing one single string in situation like this I would always use double quotes outside and then internally you can use as many single quotes as you want and it won't give you any problem similarly if you have double code inside your string use single quote outside so let's say my hollow world has double-quote then I will use single quote outside and it just works so if you print X it will print it fine all right what if now I have multi-line string let's say I would to store my address which comprises of multiple lines and my address is let's say 1 for Wall Street New York and I want to go to the next lines as soon as I hit enter I will get this error so in this situation use triple-core so triple quotes one purple Street New York is the name of my city USA and when it ends and end it with triple quotes and now when I print this address you will see that it stored it fine without any issues now that internally the way it stores it is it will use a special character so as you if you look at internal representation of this ring it is using slash and so slash and means newline now the next thing about string is you can use plus sign to concatenate two strings so if you have a string called hello and another string called Walt and if you want to join them you just do s1 plus s2 right now here I want little space in between so you can add space like this so add a space alright so plus will just join the two strings what if I want to join number with a string so let's say I want to say totals States in USA is oops I made a mistake so total states in USA so the semester and my number is 25 so I have another variable called num where I am storing total number States and I want to join these two if I do s + num it will give me this error because Python doesn't know how to join string with an integer so what you need to do first is convert this number into a string because python can join two strings so somehow con was this convert this number to a string and then join this so there is a function called STR very important you will use this a lot in Python if you lose this it will convert 25 which was a number to a string how do I know this is string you because you see this quotation mark here so now when I do s plus STR num it will print total States in USA is 25 okay so that's it that was all about strings in Python thanks for watching