Python Tutorial: Introduction to string manipulation

Key Takeaways

welcome to this course my name is O king and I will guide you in your journey to master regular expressions in this course you will learn how to manipulate strings to find and replace the specific sub strings you will also explore different approaches for a string formatting such as interpolating a string in a template last you will dive into basic and advanced regular expressions to master how to find complex patterns in a string as a data scientist you can encounter strings when cleaning a data set to prepare it for text mining or sentiment analysis some types you will need to process text to fit an algorithm but the term is whether an email is a spam maybe you will need to parse instruct specific data from a website to build a database learning to manipulate strings and master regular expressions will allow you to perform this task faster and more efficiently the first step of our journey is a strings a data type used to represent textual data Python recognizes any sequence of characters inside quotes as a single string object as shown on the slide both single or double quotes can be used you should use the same quote type to open and close the string if a quote is part of the string as seen in the code we need to use the other quote type to enclose the string otherwise Python recognizes the second quote as a closing one Python has built-in functions to handle strings suppose we define the following string we can get the number of characters in the string by applying the function alone which returns 11 are shown in the output the function st r returns the string representation of an object a scene in the code suppose now we have the following two strings shown in the slide you want to concatenate them concatenate means obtaining a new string that contains both of the original strings applying the plus operand to sum up both strings specifying also in space generates the output seen in the curve individual characters of a string can be accessed directly using an index the position of the character within the string let's work with the following example to get the fourth character of the string we specify the string name followed by the position inside square brackets in Python string indexing is zero based meaning that the first character has index 0 as shown on the slide for director for we specify in the extreme learning the following output we can also indicate indices with negative numbers if we specify index minus 1 we get the last character of the string as shown in the output with a bracket notation Python allows you to access a specific part or sequence of characters within the original string for that aim will specify the starting and ending positions inside square brackets separated by a column as you see on the slide the ending position is excluded in the resulting output omitting the first or second index results in the slide starting at the beginning or going until the end of the string as shown in the output stream of slicing also accept a third index which specifies how many characters to omit before retrieving a character in that sample the specified indices returns the following output they are the characters retrieved between positions 0 and 6 skipping two characters in between interestingly omit on the first and second indices and designating and -1 stud returns a river string as shown in the output now you are ready to start manipulating astray