Chapter 16: Managing Input/Output file

example 16.1, page no. 300

fr = open("input.txt", "r")
fw = open("output.txt", "w")
my_str = fr.readline()

for letter in my_str:
   fw.write(letter)   
#close a file
fr.close()
fw.close()

Example 16.2, page no. 303

fw = open("cities.txt", "w")
cities = ['Delhi\n','Madras\n','London\n'];
count = len(cities)
for city in cities:
    fw.write(city)   
fw.close()
fr = open("cities.txt", "r")
for line in fr.readlines():
    print line,

Delhi
Madras
London

Example 16.3 is done using CLI which is not possible in IPython Notebook

Example 16.4, page no. 305

"""
there is no bytes stream in Python. We will use normal file operations to copy from one file to another
"""

fr = open("in.txt", "r")
fw = open("out.txt", "w")
for line in fr.readlines():
   fw.write(line)       
fr.close()
fw.close()

fw = open("out.txt", "r")
for line in fw.readlines():
    print line

Java programming for internet.

Javascript for webpage develpoment.

Perl for server side scripting.

Example 16.5, page no. 307

"""
Note: In Python you can store data in file only as string.
"""

fos = open("prim.dat", "w")
fos.write(str(1999)+'\n')
fos.write(str(375.85)+'\n')
fos.write(str(False)+'\n')
fos.write("x"+'\n')
fos.close()

fis = open("prim.dat", "r")
for line in fis.readlines():
    print line
fis.close()

1999

375.85

False

x

Example 16.6, page no. 308

from random import *

dos = open("rand.dat", "w")
try:
    for i in range(20):
        dos.write(str(randint(0,100))+'\n')
except IOError:
    print IOError.message
finally:
    dos.close()

dis = open("rand.dat", "r")
# Note: random numbers are generated so output will differ from that given in the textbook.
for line in dis.readlines():
    print line,

92
49
68
67
71
25
85
53
10
87
15
5
33
30
72
52
80
85
36
84

Example 16.7, page no. 310

file1 = open("file1.txt", "r")
file2 = open("file2.txt", "r")
file3 = open("file3.txt", "a")

for line in file1.readlines():
    file3.write(line)
for line in file2.readlines():
    file3.write(line)
    
file1.close()
file2.close()
file3.close()

Example 16.8, page no. 312

fp = open("random.dat", "w+")
fp.write("x\n")
fp.write(str(555)+'\n')
fp.write(str(3.1412)+'\n')
fp.seek(0)
print fp.readline()
print fp.readline()
print fp.readline()
fp.seek(2)
print fp.readline()
fp.seek(fp.tell()+len(fp.readline()))
fp.write("False\n")
fp.seek(13)
print fp.readline()
fp.close()

x

555

3.1412

555

False

Example 16.9, page no. 314

fp = open("cities.txt", "a")
fp.write("Mumbai\n")
fp.close()

Example 16.10, page no. 315

dos = open("invent.dat", "w")
dos.write(raw_input("Enter code number: ")+'\n')
dos.write(raw_input("Enter number of items: ")+'\n')
dos.write(raw_input("Enter cost: ")+'\n')
dos.close()
dis = open("invent.dat", "r")
codeNumber = int(dis.readline())
totalItems = int(dis.readline())
itemCost = int(dis.readline())
totalCost = totalItems*itemCost
dis.close()

print "Code Number: ", codeNumber
print "Item Cost: ", itemCost
print "Total Items: ", totalItems
print "Total Cost: ",  totalCost

Enter code number: 1001
Enter number of items: 193
Enter cost: 452
Code Number:  1001
Item Cost:  452
Total Items:  193
Total Cost:  87236