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CSCA20H3 Study Guide - Final Guide: Backslash

Computer Science
Course Code
Anna Bretscher
Study Guide

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CSCA20 General Programming
1. Files
a. Open a file:
To read
open_file = open(‘filename.txt’, ‘r’)
To write – replaces file filename
open_file = open(‘filename.txt’, ‘w’)
To append
open_file = open(‘filename.txt’, ‘a’)
b. Close file after finishing:
c. Reading Files:
my_file = open(‘filename’, ‘r’)
# Retrieving individual data
for line in my_file:
# split each word/data at whitespace
each_line = line.split()
# indexed line refers to all data in column ‘i’
specific_data = each_line[i]
# Read whole file at once as list of strings
list_of_lines = my_file.readlines()
# Read file one line at a time
line = my_file.readline()
# Read entire file as a string
s =
# Read specific number of characters
s = reads 10 characters
s = reads next 10 characters
2. Reading from a CSV(comma-separated values) file
import io
import csv
csv_file = open(‘csv_filename.csv’, ‘r’)
reader = csv.reader(csv_file)
for line in reader:
# read like an ordinary file
# but each line is a list
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