You’ll learn how to read CSV files in Python in this lesson, along with how to convert them to Python lists and dictionaries. When it comes to reading CSV files, the Python csv library is very flexible. For instance, you can read CSV files into Python lists while utilizing custom delimiters and reading headers. CSV files may also be read into Python dictionaries.
After reading this guide, you will have acquired the following knowledge:
- To read csv file in python, use the csv.reader() and csv.DictReader() methods.
- How to open CSV files and change them into Python dictionaries and lists
- How to handle typical problems like double quotes, encoding variations, and escape characters
How to Read CSV Files into a Python List Immediately
The code that follows can be useful if you need to quickly read a CSV file into lists. The example’s code only prints the lists. They might also be added to a list to create a list of lists.
Importing a CSV File as Lists is the quick response.
file open(‘file.csv’, ‘r’):
Row in reader for: Reader = CSV.Reader(File, Row),
[‘Nik’, ’34’, ‘datagy.io’, ‘Toronto’] returns the following value.
# (‘Kate’, ’33’, ‘Google’, ‘Paris’)
# “Evan,” “32,” “bing,” “New York City”
# (‘Kyra’, ’35’, ‘yahoo’, ‘Atlanta’)
When it comes to reading CSV files, the Python csv module library is incredibly flexible. Throughout this tutorial, we’ll examine how to parse CSV files into lists and dictionaries. We’ll also discuss how to customize how CSV files are read, including how to handle different delimiters and encodings.
Python Instructions for Reading a CSV File to a List
This section will discuss using Python to read a CSV file into a list or a collection of lists. Investigating the csv.reader class, which returns a generator based on the file input, will be used to do this. Additionally, we’ll look at how to read files with a header row (and how to skip it) and how to read all lines at once.
Read a CSV file into a list line by line in Python
Python’s csv.reader class can be used to loop through each row of a CSV file and read the data into a list. Let’s check out how Python handles this. We’ll be using a CSV file like the one below for our work:
- Nik,34,datagy.io,Toronto
- Kate,33,google,Paris
- 32-year-old New Yorker Evan
- Kyra,35,yahoo,Atlanta
This could appear unnecessary in a few ways. If you know you’re going to read every row in the dataset and want to save it in a single data structure, there is a simpler way to achieve this. We’ll examine how we could modify our code to accomplish this in the section that follows.
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Read a CSV file in Python and add each line to a list of lists
To read every line from a CSV file into a Python list of lists, we can simply pass the reader object into the list() function. Depending on the size of your CSV file, this can cause some memory issues because you’ll be unpacking the entire generator object at once.
How to Read a Header from a CSV File into a Python List
When examining a CSV file with a header, we have three options:
- The same list of lists as before is read with the heading.
- Maintain a separate list for the heading.
- Eliminate the heading completely.
To read the heading into the list of lists, we don’t need to make any changes to the preceding example.
The following method can be used to read the heading into a separate list. With this, the heading is added to one list, and the subsequent rows are added to another.
By doing so, the heading is given its own list header. The next() function, which reads the initial item, is used in this circumstance. As the second argument, we pass None, which deals with the situation where no record is safely present.
The remaining information is then read into a list of lists row by row. If you wish to save the header information and need to refer to it later, this can be helpful.
How are these going to be printed?
Python f-strings are being used in this case to output the elements. Despite the fact that f-strings have been around since Python 3.6, the strategy we’re using was only introduced in Python 3.8. The print(f’var=’) method, which prints the variable name and any values it contains, is used to facilitate debugging.
Conclusion
In this guide, you learned how to read CSV files into lists and dictionaries using Python. The Python csv library has a wide range of options for reading CSV files. The module gives you reader objects for both lists and dictionaries so you may customize the output of your CSV file.
The first thing you learned was how to read CSV files to lists, which involved reading a single row, several rows, and adding headers. Then you covered the same terrain again while dealing with Python dictionaries and the extra options made available by the DictReader class. In the end, you learned how to change behavior by experimenting with different options including changing delimiters and double quoting, as well as creating dialects for convenient reuse.
