1. Use Python basic syntax to read and write CSV files
The general idea of reading the data in the CSV file with basic syntax is: get the file object, read the table header, split the header field according to the comma separator, use the for loop statement to get the record data of the table body, and write it into another file after splitting In a CSV file (if you want to write data into a file in xls* format, please refer to the previous official account article), the steps are as follows:
Step 1: Import the necessary modules to obtain the input and output file paths.
import sys
infile = sys.argv[1]
outfile = sys.argv[2]
Step 2: Use the open built-in function to get the file object.
with open(infile, “r”, newline=‘’) as fr, open(outfile, “w”,
newline=‘’) as fw:
Step 3: Use the readline method of the file object or the next method of the iterator to read the table header (the file object is an iterator object that supports the iteration protocol), and use the str.split method to split the table header (note, use strip function to remove the trailing newline).
header = next(fr)
header = header.strip()
header_list = header.split(“,”)
Step 4: Now that the table header has been checked and divided, we need to write the table header into the file object (note that a newline character needs to be added at the end).
fw.write(“,”.join(map(str, header_list)) + “\n”)
Of course, the above code can also be written like this:
print(*header_list, sep=“,”, file=fw)
Step 5: Use the for loop to read the table body data, split it into a list and write it to the file.
for row in fr:
row = row.strip()
row_list = row.split(“,”)
fw.write(“,”.join(map(str, header_list)) + “\n”)
After the above steps are completed, enter in the command prompt:
python csvrw.py inputfile.csv outputfile.csv
Please customize the input and output csv file names and script names, the above are just examples.
The above code is as follows:
Use pandas to read and write CSV files
2. Use pandas to read and write CSV files
The pandas library is a powerful data processing and data analysis library. It is easier to use pandas to process csv files. The steps are as follows:
Step 1: First, import the necessary modules to obtain the input and output file paths.
import sys
import pandas as pd
infile = sys.argv[1]
outfile = sys.argv[2]
Step 2: Use the read_csv method of pandas to store the data into a DataFrame object.
dataframe = pd.read_csv(infile)
Step 3: Then use the to_csv method of DataFrame to output it to another csv table.
dataframe.to_csv(outfile, index=False)
After the above steps are completed, enter the corresponding command in the command prompt (please refer to <2>)
code show as below:
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