Python IO

Deanne

Keyboard input

myStr = input("Enter your input: ")
print("Your answer is: ")

File object

open function creates a Python file object which links to a file on your machine

Once open, strings of data can transferred to and from the file

To open a file:

afile = open(filename, mode)
afile.method

The mode can be 'r' for read, 'w' for write, or 'a' to append

Common file operations

Example

# Write a file
out_file = open("test.txt", "w")
out_file.write("This Text is going to out_file\nLook at it and see!")
out_file.close()

# Read a file
in_file = open("test.txt", "r")
text = in_file.read()
in_file.close()

print(text)

Reading csv files

import csv

f = open("file path", 'r') #input the file path for the PracticeFile.csv
try:
    reader = csv.reader(f)
    for row in reader:
        print(row)
finally:
    f.close()

Writing to csv files

import csv

f = open('yourFileName.csv', 'w', newline='')
try:
    writer = csv.writer(f)
    writer.writerow(('Title 1', 'Title 2', 'Title 3'))
    for i in range(10):
        writer.writerow((i+1, chr(ord('a') + i), '08/%02d/07' % (i+1)))
finally:
    f.close()

print(open('yourFileName.csv', 'r').read())

Reading csv as dictionary

import csv

f = open('file path', 'r')
try:
    reader = csv.DictReader(f)
    for row in reader:
        print(row)
finally:
    f.close()

Writing dictionary to csv

import csv

f = open('myDictionary.csv', 'w', newline='')
try:
    fieldnames = ('Title 1', 'Title 2', 'Title 3')
    writer = csv.DictWriter(f, fieldnames=fieldnames)
    headers = dict((n, n) for n in fieldnames)
    writer.writerow(headers)
    for i in range(10):
        writer.writerow({ 'Title 1': i+1,
                          'Title 2': chr(ord('a') + i),
                          'Title 3': '08/%02d/07' % (i+1),
                          })
finally:
    f.close()

print(open('myDictionary.csv', 'r').read())

Conversion from strings

Datafile

Python file

Pickles!!

Python file