Type Casting In Python

University:
California State University, Chico
Course:
CSED 590 | Software Design, Data Structures, and Algorithms
Academic year:

2024
Views:

0

Pages:

8
Author:

Sanchit Kumar

Python programming Type Casting In Python Sometimes in our program, it is necessary for us to convert from one data type to another, such as from an integer to a string. This is known as type casting. There are three built-in functions in Python that allow us to do type casting. These are the int(), float(), and str() functions. The int() function in Python takes in a float or an appropriate string and converts it to an integer. To change a float to an integer, we can type int(5.712987). We’ll get 5 as the result (anything after the decimal point is removed). To change a string to an integer, we can type int (“4”) and we’ll get 4. However, we cannot type int (“Hello”) or int (“4.22321”). We’ll get an error in both cases. The float() function takes in an integer or an appropriate string and changes it to a float. For instance, if we type float(2) or float(“2”), we’ll get 2.0. If we type float(“2.09109”), we’ll get 2.09109 which is a float and not a string since the quotation marks are removed. The str() function on the other hand converts an integer or a float to a string. For instance, if we type str(2.1), we’ll get “2.1”. Now that we’ve covered the three basic data types in Python and their casting, let’s move on to the more advanced data types. List List refers to a collection of data which are normally related. Instead of storing these data as separate variables, we can store them as a list. For instance, suppose our program needs to store the age of 5 users. Instead of storing them as user1Age, user2Age, user3Age, user4Age and user5Age, it makes more sense to store them as a list. To declare a list, you write listName = [initial values]. Note that we use square brackets [ ] when declaring a list. Multiple values are separated by a comma. Example: userAge = [21, 22, 23, 24, 25] We can also declare a list without assigning any initial values to it. We simply write listName = []. What we have now is an empty list with no items in it. We have to use the append() method mentioned below to add items to the list. Individual values in the list are accessible by their indexes, and indexes always start from ZERO, not 1. This is a common practice in almost all programming languages, such as C and Java. Hence the first value has an index of 0, the next has an index of 1 and so forth. For instance, userAge[0] = 21, userAge[1] = 22 Alternatively, you can access the values of a list from the back. The last item in the list has an index of -1, the second last has an index of -2 and so forth. Hence, userAge[-1] = 25, userAge[-2] = 24. You can assign a list, or part of it, to a variable. If you write userAge2 = userAge, the variable userAge2 becomes [21, 22, 23, 24, 25]. Tuple Tuples are just like lists, but you cannot modify their values. The initial values are the values that will stay for the rest of the program. An example where tuples are useful is when your program needs to store the names of the months of the year. To declare a tuple, you write tupleName = (initial values). Notice that we use round brackets ( ) when declaring a tuple. Multiple values are separated by a comma. Example: monthsOfYear = (“Jan” , “Feb” , “Mar” , “Apr” , “May” , “Jun” , “Jul” , “Aug” , “Sep” , “Oct” , “Nov” , “Dec”) You access the individual values of a tuple using their indexes, just like with a list. Hence, monthsOfYear[0] = “Jan” , monthsOfYear[-1] = “Dec”. For more examples of what you can do with a tuple, check out Appendix C.

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