 My name is Sandesh Pare. I am currently working as an assistant professor in the Department of Computer Science and Engineering at Vachan Institute of Technology, Sulapur. And in this video we are going to focus on the variables in the Python. So, before going to start the implementation regarding the Python, we will check the first what will be the outcome of this session. So, at the end of this video, you will be able to use different types of the variables in the program. So, let us start to implement the variables. Generally, x is the variable, let us say, and we will give one value to this one. Let us say x is equal to 2. It worked. No output of this one because it is the assignment operator. The value is assigned to it. If you want to check the contents of the x, then you have to just write x and you have to press enter. The value is displayed here. And again, any operation regarding the variables, if you want to perform, then you may do it x plus 3, let us say, and it will give you the value 5. And I will use the second variable that is y is equal to 3 here. It is also working. So, contents of y is 3. And now, I just want to add these both variables that is x plus y. So, the value is 5. In this fashion, the variables get added here and the result is displayed. So, in this fashion, variables are used here. And as we have discussed earlier that Python is a robust one. It means we do not need to specify the data type of the variable here. So, based on the value which is assigned to this, it will understood automatically that what is the data type of the variable. And again, I just want to tell you here one special thing that suppose 5 is our recent output. If you want to use this one and if you want to add the contents of the y to the recent output, so what you have to do is that you have to just use the underscore operator. Underscore will give you the last output generated. Let us say plus y. So, as you can see, the output is 8. So, 5 plus 3 is 8. So, in this fashion, you can use the underscore to access the last generated output. x and y are now defined. So, that is why it is working properly. Let us say z. It is not defined yet. If you want to try to access the contents of z, if you want to display the contents of z, so as you can see the error is arised here because it is not defined yet. So, this is happening regarding the variable. Now, we are storing the integer type of data in the variable. So, we will change this one. We will assign the string values to the variables now. Let us say the variable name. Name is equal to, let us say value is YouTube. Name is equal to YouTube and it is working totally fine. No problem in that one. So, let us say I just want to append one more string to this variable. So, for that you have to use the plus operator there. So, let us say name plus, let us say YouTube rocks. So, yes, as you can see it get appended there. But value of the name is YouTube only. You can cross verify it. So, do not get confused between that. And that plus operator is very important. Without that, it will not work. If you want to check it, then I will show you the demo that I will remove the plus operator. We will simply write this like that. So, invalid syntax. That plus operator is very important. Otherwise, it will not perform the concatenation there. And again, I just want to tell you that indexing concept is used here. This variable is now containing the string. It means it is the sequence of the characters. So, the indexing technique is used to particularly access one of the character from that string there. So, for that, let us say, suppose name of 6. So, as you can see the letter E is displayed here. Because it is the last index, right? 0 to 6. Total 7 letters are there in the YouTube. So, it is written here. And again, if you want to provide the negative index value, it is also working. So, if suppose let us say name of minus 2, right? So, B is the output because when you pass the negative number as the index, it started traversing from the end in the reverse fashion. And it starts from the minus 1. E is the minus 1. So, B is the minus 2. And one more thing is that you can pass the range also in the indexing. Let us say name of 0, let us say 3. So, first is the starting index of the substring. That is 0. And 3 is the ending index. And it will exclude it. Just keep in mind that when you start, it will be included. But when you will ending index is here, it will be excluded. 0, 1, 2. These 3 index values are written here. That is y, o, u. Third index is excluded. Just keep in mind. Do not get confused between each. And suppose you have passed, now the 7 letters are there in the YouTube. And that was 0 to 6 index values are there. What will happen if you pass the particular out of range value as the term here? Let us say it. So, it will arise the index error. So, you have to pass this in between the range. So, there is one question for you guys that what is the operator which is used to fetch which is lastly generated output in the Python programming language. Just think about it and answer. So, the answer is the underscore operator. As we have seen in the integer addition, the underscore operator is used to fetch the last result which is generated by the Python programming language. And based on that, you can perform any further operations. So, let us move to the Python again. Now, we are using the range as the indexing here. And what will happen if you did not specify the ending of this range here? Let us say, name of the range. So, let us say, name of, I will mention the start, but I will not mention the end here. Then it will go up to the end of the main string. So, again in the reverse fashion, if you did not mention the starting of the range, suppose let us say 3, then it will start from the beginning of the string by defaulting and it will go up to the whatever the ending index provided there, but it will exclude that index. Just keep in mind, I am just repeating that instruction again and again. And what will happen if particular index is out of range there, means while specifying the range. Let us say, name of, suppose it will starting from the 3, but it will end at the 10, suppose let us say, but the actual index is up to the 6 there, 0 to 6. I will specify 10 here and let us check what is the output of this one. So, as you can see, the output is displayed here. So, no any error is arise here. But the traversal is goes to end of the string and it will terminate there automatically. And I just want to tell you that these variables what you are using that string integer, these are immutable. So, if you assigned it one times, though you cannot make any changes to them. So, let us say instead of the U2, I just want to make it a mount U. So, I will remove the, otherwise I will say I will overwrite the y to the m. Instead of y, I just want m there. So, I want to make it mount U. So, I will try name of 0 as the y is at 0 th index, name of 0. Let us assign m here to this name of 0. So, let us check it is working or not. As you can see, the error is arise here because string object does not support item assignment because it is immutable. So, once you have created it, once you have defined it, you cannot make any further changes in this one. So, that is why it is called as the immutable. And one more function that is, let us say if you want to find the length of that particular string, then there are some input methods are given just like the name and length of name. You just want to find the length of name here. So, as you can see the output is 7. So, likewise some input methods are provided here to get various outputs related to these variables. And yeah, this is related the variables and these are some references I used to make these videos. Thank you.