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Key Concepts
Review core concepts you need to learn to master this subject
Pandas
Pandas
Pandas is an open source library that is used to analyze data in Python. It takes in data, like a CSV or SQL database, and creates an object with rows and columns called a data frame. Pandas is typically imported with the alias pd.
Pandas DataFrame creation
Pandas DataFrame creation
The fundamental Pandas object is called a DataFrame. It is a 2-dimensional size-mutable, potentially heterogeneous, tabular data structure.
A DataFrame can be created multiple ways. It can be created by passing in a dictionary or a list of lists to the pd.DataFrame() method, or by reading data from a CSV file.
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Pandas is a Python module for working with tabular data (i.e., data in a table with rows and columns). Tabular data has a lot of the same functionality as SQL or Excel, but Pandas adds the power of…
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A DataFrame is an object that stores data as rows and columns. You can think of a DataFrame as a spreadsheet or as a SQL table. You can manually create a DataFrame or fill it with data from a CSV, …
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You can also add data using lists. For example, you can pass in a list of lists, where each one represents a row of data. Use the keyword argument […] to pass a list of column names. […..
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We now know how to create our own DataFrame. However, most of the time, we’ll be working with datasets that already exist. One of the most common formats for big datasets is the CSV. *CSV (com…
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When you have data in a CSV, you can load it into a DataFrame in Pandas using […] : […] In the example above, the […] method is called. The CSV file called […] is passed in as an a…
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When we load a new DataFrame from a CSV, we want to know what it looks like. If it’s a small DataFrame, you can display it by typing […] . If it’s a larger DataFrame, it’s helpful to be able t…
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Now we know how to create and load data. Let’s select parts of those datasets that are interesting or important to our analyses. Suppose you have the DataFrame called […] , which contains the a…
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When you have a larger DataFrame, you might want to select just a few columns. For instance, let’s return to a DataFrame of […] from ShoeFly.com: |id|first_name|last_name|email|shoe_type|s…
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Let’s revisit our […] from ShoeFly.com: |id|first_name|last_name|email|shoe_type|shoe_material|shoe_color| | — | — | — | — | — | — | — | |54791|Rebecca|Lindsay|RebeccaLindsay5…
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You can also select multiple rows from a DataFrame. Here are a few more rows from ShoeFly.com’s […] DataFrame: |id|first_name|last_name|email|shoe_type|shoe_material|shoe_color| |-|-|-|-|-…
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You can select a subset of a DataFrame by using logical statements: […] We have a large DataFrame with information about our customers. A few of the many rows look like this: |name|addre…
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You can also combine multiple logical statements, as long as each statement is in parentheses. For instance, suppose we wanted to select all rows where the customer’s age was under 30 or the cus…
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Suppose we want to select the rows where the customer’s name is either “Martha Jones”, “Rose Tyler” or “Amy Pond”. |name|address|phone|age| |-|-|-|-| |Martha Jones|123 Main St.|234-567-8910|2…
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When we select a subset of a DataFrame using logic, we end up with non-consecutive indices. This is inelegant and makes it hard to use […] . We can fix this using the method […] . For exam…
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You’ve completed the lesson! You’ve just learned the basics of working with a single table in Pandas, including: - Create a table from scratch - Loading data from another file - Selecting certain …
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In the previous lesson, you learned what a DataFrame is and how to select subsets of data from one. In this lesson, you’ll learn how to modify an existing DataFrame. Some of the skills you’ll lea…
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Sometimes, we want to add a column to an existing DataFrame. We might want to add new information or perform a calculation based on the data that we already have. One way that we can add a new co…
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We can also add a new column that is the same for all rows in the DataFrame. Let’s return to our inventory example: |Product ID|Product Description|Cost to Manufacture|Price| |————–|–…
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Finally, you can add a new column by performing a function on the existing columns. Maybe we want to add a column to our inventory table with the amount of sales tax that we need to charge for eac…
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In the previous exercise, we learned how to add columns to a DataFrame. Often, the column that we want to add is related to existing columns, but requires a calculation more complex than multiplic…
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A lambda function is a way of defining a function in a single line of code. Usually, we would assign them to a variable. For example, the following lambda function multiplies a number by 2 and t…
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We can make our lambdas more complex by using a modified form of an if statement. Suppose we want to pay workers time-and-a-half for overtime (any work above 40 hours per week). The following fun…
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In Pandas, we often use lambda functions to perform complex operations on columns. For example, suppose that we want to create a column containing the email provider for each email address in the f…
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We can also operate on multiple columns at once. If we use […] without specifying a single column and add the argument […] , the input to our lambda function will be an entire row, not a col…
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When we get our data from other sources, we often want to change the column names. For example, we might want all of the column names to follow variable name rules, so that we can use […] …
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You also can rename individual columns by using the […] method. Pass a dictionary like the one below to the […] keyword argument: […] Here’s an example: […] The code above will re…
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Great job! In this lesson, you learned how to modify an existing DataFrame. Some of the skills you’ve learned include: - Adding columns to a DataFrame - Using lambda functions to calculate comple…
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Stress-test your knowledge with quizzes that help commit syntax to memory
Creating, Loading, and Selecting Data with Pandas
Consider the following code that is intended to create a new DataFrame showing the grades of students in a class. Will this code create a valid DataFrame? If not, why?
Modifying DataFrames
Consider the following DataFrame showing the daily inventory and amount of products sold of a local office supply store. You want to add a column to this DataFrame to determine how many of each item is remaining at the end of the day. Which of the following lines of code would accomplish this?