DATA 301: Data Analytics (2) Python File Input/Output DATA 301 Many data processing tasks require reading and writing to files. Introduction to Data Analytics I/O Type Python Data Analytics Open a file for reading: infile = open("input.txt", "r") Dr. Ramon Lawrence Open a file for writing: University of British Columbia Okanagan outfile = open("output.txt", "w")
[email protected] Open a file for read/write: myfile = open("data.txt", "r+") DATA 301: Data Analytics (3) DATA 301: Data Analytics (4) Reading from a Text File (as one String) Reading from a Text File (line by line) infile = open("input.txt", "r") infile = open("input.txt", "r") for line in infile: print(line.strip('\n')) val = infile.read() Read all file as one string infile.close() print(val) infile.close() Close file # Alternate syntax - will auto-close file with open("input.txt", "r") as infile: for line in infile: print(line.strip('\n')) DATA 301: Data Analytics (5) DATA 301: Data Analytics (6) Writing to a Text File Other File Methods outfile = open("output.txt", "w") infile = open("input.txt", "r") for n in range(1,11): # Check if a file is closed outfile.write(str(n) + "\n") print(infile.closed)# False outfile.close() # Read all lines in the file into a list lines = infile.readlines() infile.close() print(infile.closed)# True DATA 301: Data Analytics (7) DATA 301: Data Analytics (8) Use Split to Process a CSV File Using csv Module to Process a CSV File with open("data.csv", "r") as infile: import csv for line in infile: line = line.strip(" \n") with open("data.csv", "r") as infile: fields = line.split(",") csvfile = csv.reader(infile) for i in range(0,len(fields)): for row in csvfile: fields[i] = fields[i].strip() if int(row[0]) > 1: print(fields) print(row) DATA 301: Data Analytics (9) DATA 301: Data Analytics (10) List all Files in a Directory Python File I/O Question Question: How many of the following statements are TRUE? import os print(os.listdir(".")) 1) A Python file is automatically closed for you.