1、 Read CSV file
Using the CSV module to read CSV files in Python is very simple. After importing the CSV module, the CSV. reader() function can be used to directly read data from the CSV file. Here is an example code:
In the above code, we first import the CSV module. Then, use the with open() function to read the CSV file and create a CSV reader object that will read each line in the CSV file using a comma separator and print each line of data.
2、 Write CSV file
Similar to reading a CSV file, using the CSV module to write data to the CSV file is also very simple. Here is an example code:
In the above code, we use the with open() function to create a CSV writer object and use the writerow() function to write the data line by line into the CSV file. Among them, the newline='' parameter can prevent unnecessary blank lines from appearing in the CSV file.
3、 Handling missing values and special characters in CSV files
When reading CSV files, we sometimes encounter missing values or special characters. To prevent data errors, we need to address these issues.
1. Handling missing values:
In CSV files, missing values are usually represented by NaN or spaces. In Python, we can use the Pandas library's read_ The csv() function reads the csv file and uses the dropna() function to delete lines with missing values:
2. Handling special characters:
In CSV files, some special characters may disrupt the data structure and affect subsequent data processing and analysis. In Python, we can use the quotechar and quoting parameters of the CSV module to handle special characters.
In the above code, we used quotechar='"' to specify the quotation mark character in the CSV file as double quotation marks, and used the quoting parameter to specify csv.QUOTEMINIMAL, which means preserving the original data structure as much as possible.
4、 Batch processing of CSV files using Pandas
In addition to using the CSV module, we can also use the read in the Pandas library_ The csv() function reads and processes a large number of csv files. In Pandas, we can use the DataFrame data structure to batch process CSV files.
In the above code, we used the global module to match all files ending in CSV and used read_ The csv() function reads data from a csv file. Then, use the concat() function to merge all the data into a DataFrame data structure.
