Lecture Note
University
University of California San DiegoCourse
DSC 207R | Python for Data SciencePages
5
Academic year
2023
anon
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26
Live Code, Why pandas Unlocking the Full Potential of Pandas Library in Python If you are a data scientist or analyst, you must have come across Pandas library in Python at some point. This powerful tool is essential for data manipulation and analysis in Python.With Pandas, you can easily import, clean, manipulate, and merge large data sets with just afew lines of code. In this article, we will delve into the two main data structures in Pandas, the Pandas Series and the Pandas DataFrame. We will also explore how to import Pandas into our notebookand how to use it to manipulate data. Importing Pandas into Your Notebook Before we dive into the details of Pandas data structures, let us first import Pandas into our notebook. Open your Introduction to Pandas notebook in your folder for Week Four andfollow along. To import Pandas, we use the line of code "import pandas as pd." This line of code tells Python to import the Pandas module and rename it to "pd" for ease of use. Creating a Pandas Series Now that we have imported Pandas into our notebook let's start with Pandas Series. A series is a one-dimensional labeled array that can hold any data type such as integers,strings, and floats. It is similar to a NumPy array but with the added advantage of being ableto define index labels together with the data. import pandas as pdser = pd.Series(data=[1, 2, 3, 4, 5], index=['tom', 'bob', 'nancy', 'dan', 'eric'])print(ser) Here, we have created a series object called ser with data equal to an array of integers [1, 2, 3, 4, 5] and index equal to a list of strings ['tom', 'bob', 'nancy', 'dan', 'eric']. When we runthis code, we get the following output: tom 1 bob 2 nancy 3
dan 4 eric 5 dtype: int64 As you can see, the output shows the data array indexed by the names we put in our data structure instead of the default zero through four indices. This makes it easier to work withdata, especially when dealing with large datasets. We can also create a Pandas series without specifying the data and index labels. Pandas can infer the data and index labels from the array we provide as follows: import pandas as pdser = pd.Series([1, 2, 3, 4, 5])print(ser) Unlocking the Full Potential of Pandas Library in Python If you are a data scientist or analyst, you must have come across Pandas library in Python at some point. This powerful tool is essential for data manipulation and analysis in Python.With Pandas, you can easily import, clean, manipulate, and merge large data sets with just afew lines of code. In this article, we will delve into the two main data structures in Pandas, the Pandas Series and the Pandas DataFrame. We will also explore how to import Pandas into our notebookand how to use it to manipulate data. Importing Pandas into Your Notebook Before we dive into the details of Pandas data structures, let us first import Pandas into our notebook. Open your Introduction to Pandas notebook in your folder for Week Four andfollow along. To import Pandas, we use the line of code "import pandas as pd." This line of code tells Python to import the Pandas module and rename it to "pd" for ease of use. Creating a Pandas Series Let's start with the Pandas Series now that we have loaded Pandas into our notebook. Any data type, including texts, floats, and integers, can be stored in a series, which is aone-dimensional named array. It is comparable to a NumPy array but has the advantage ofallowing index labels to be defined along with the data. We can create a Pandas series using the following code:
pythonCopy codeimport pandas as pdser = pd.Series(data=[1, 2, 3, 4, 5], index=['tom', 'bob', 'nancy', 'dan', 'eric'])print(ser) Here, we have created a series object called ser with data equal to an array of integers [1, 2, 3, 4, 5] and index equal to a list of strings ['tom', 'bob', 'nancy', 'dan', 'eric']. When we runthis code, we get the following output: pythonCopy codetom 1 bob 2 nancy 3dan 4 eric 5 dtype: int64 As you can see, the result displays the data array with the names we gave it in our data structure as indexes rather than the standard zero through four. This makes working withdata simpler, especially when working with big datasets. We can also create a Pandas series without specifying the data and index labels. Pandas can infer the data and index labels from the array we provide as follows: pythonCopy codeimport pandas as pdser = pd.Series([1, 2, 3, 4, 5])print(ser) Here, we get the same output as before because Pandas knows how to resolve the two arrays into a series data structure. Accessing Data in a Pandas Series Any of the indices can be used to retrieve data by enclosing it in a set of rectangular brackets. For example, to get the value linked with the 'nancy' index, we can use thefollowing code: print(ser['nancy']) This will return the value 3 associated with the 'nancy' index. Manipulating Data in a Pandas Series
Pandas provides a wide range of methods for manipulating data in a Pandas Series. For example, we can use the following code to add two Pandas series together: ser1 = pd.Series([1, 2, 3, 4, 5])ser2 = pd.Series([10, 20, 30, 40, 50])ser3 = ser1 + ser2print A popular open-source data manipulation library for Python is called Pandas. It offers high-level data structures and functions for working with structured data, making it a potenttool for data analysis. NumPy, another well-liked Python library for scientific computing, is thefoundation upon which Pandas is constructed. In-depth examination of the creation ofPandas Series and Dataframe objects, as well as some of the fundamental actions that maybe carried out on them, are covered in this article. Creating a Pandas Series A Pandas Series is a one-dimensional labeled array that can hold any data type, including integers, floating-point numbers, strings, and more. Series objects are indexed by a set oflabels, which can be strings or integers. The index provides a label for each data point,making it easy to reference and manipulate the data. To create a Pandas Series, you can pass a list or an array of values to the Series constructor. For example, let's create a Series of integers from 0 to 4: import pandas as pd ser = pd.Series([0, 1, 2, 3, 4]) Alternatively, you can create a Series using a dictionary. The keys of the dictionary will be used as the index labels, and the values will be the data points in the Series. For example: d = {'apple': 0, 'banana': 1, 'cherry': 2}ser = pd.Series(d) In this example, the index labels are strings ('apple', 'banana', 'cherry'), and the data points are integers (0, 1, 2). You can also create a Series with custom index labels by passing a listof labels as the second argument to the constructor. For example: ser = pd.Series([0, 1, 2], index=['apple', 'banana', 'cherry']) Accessing Data in a Pandas Series
Once you have created a Pandas Series, you can access the data using the index labels. There are several ways to do this. The most common way is to use the square bracketnotation with the index label inside the brackets. For example, if we have a Series ser withindex labels 'apple', 'banana', and 'cherry', we can access the data at the 'banana' labelusing ser['banana']. ser = pd.Series([0, 1, 2], index=['apple', 'banana', 'cherry'])print(ser['banana']) # Output: 1 Alternatively, you can use the loc method to access data using the index label. For example: print(ser.loc['banana']) # Output: 1 If you want to access multiple data points at once, you can pass a list of index labels to the square bracket notation or the loc method. For example: print(ser[['apple', 'banana']]) # Output: apple 0\nbanana 1\ndtype: int64 print(ser.loc[['apple', 'banana']]) # Output: apple 0\nbanana 1\ndtype: int64 You can also access data using integer indices using the iloc method. The iloc method works similar to the loc method, but it takes integer indices instead of index labels. Forexample: print(ser.iloc[1]) # Output: 1print(ser.iloc[[0, 1]]) # Output: apple 0\nbanana 1\ndtype: int
Exploring Data Manipulation and Analysis with Live Code Examples
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