10 Python file.pptx

x=open(“Smahi.txt”,
“w”)
A file memory x created in RAM, and get
connected to a file called “Smahi.txt” in
overwrite mode, which is available in
same folder, if the file not found, it will be
created automatically.

x=open(“Smahi.txt”,“w”)
x.write(“Debanshi ” )
connected to a file called “Smahi.txt”, in
overwrite mode, which is available in
same folder, if the file not found, it will be
created automatically. A string called
“Debanshi ” is written in file memory.

x=open(“Smahi.txt”, “w”)
x.write(“Debanshi ” )
x.close()
connected to a file called “Smahi.txt”,
which is available in same folder, if the file
not found, it will be created automatically.
A string called “Debanshi ” is written in
file memory. Now to transfer the contents
of the file memory to the file “Smahi.txt”
we have to disconnect the file memory x
with “Smahi.txt” using the close()

y=“Debanshi ”
x.write(y)
x.close()
A string variable y is created and
initialized with “Debanshi ”, after
that the same is written in file
memory x from which the contents is
transferred to the file “Smahi.txt”
using the function close()

y=“Debanshi ”
x.write(y)
x.close()
Remember we can
store only string in
file

y=23759
x.write(y)
x.close()
Argument of write()
must be str not int.

x.write(“Debanshi ”)
x.write(“Sampurna ”)
x.close()
Output:
Debanshi Sampurna

x.write(“Debanshi n”)
x.close()
Output:
Debanshi
Sampurna

x.write(“Debanshi t”)
x.close()
Output:
Debanshi Sampurna

x.writelines(“Debanshi ”)
x.writelines(“Sampurna ”)
x.close()
Another technique to
write in a file

x.writelines(“Debanshi ”)
x.close()
Output:
Debanshi Sampurna

x.writelines(“Debanshi n”)
x.close()
Output in a file:
Debanshi
Sampurna

x=open("Smahi.txt","w")
y=["Debanshi","Sampurna","Riya
"]
x.write(y)
x.close()
Argument in write
must be string, not list

Its Okay, Output will
be
Debanshi Sampurna Riya

write() is used to
write string,
whereas writelines()
is used to write list
or string

for y in range(4):
x.write(input("Enter name "))
x.close()
Program will accept 4
names and store in a
file called “Smahi.txt”

for y in range(4):
x.write(input("Enter name
")+‘n’)
x.close()
Program will accept 4
names and store in a file
in separate lines, called
“Smahi.txt”

z=[]
for y in range(4):
z.append(input("Enter name
")+'n')
x.writelines(z)
x.close()
Program will accept 4 names
and store in a file in separate
lines, called “Smahi.txt”

z=[]
for y in range(4):
z[y].append(input("Enter name ")+'n')
x.writelines(z)
x.close()
Error:
Instead of z[y], we have to
write z

z=[]
for y in range(4):
z.append(input("Enter name ")+'n')
x.write(z)
x.close()
Error:
write() is used to input string
not the list

w is used to create
the file in overwrite
mode, whereas a is
used to create the
file in append mode

x=open("Smahi.txt","a")
z=[]
for y in range(4):
")+'n')
x.writelines(z)
x.close()
Initially if the file contains
Amit
Sumit
New names will be added after
Sumit

x=open("Smahi.txt","a")
z=[]
for y in range(4):
")+'n')
x.writelines(z)
x.close()
Initially if the file contains
nothing, New names will be
added from beginning of the
file

x=open("Smahi.txt",“r")
y=x.read()
print(y)
x.close()
Output:
Ram
Shyam
Let the contents of the file Smahi.txt is
Ram
Shyam

Warning
If the file we are trying to
open for reading is not
present in the disk, in
that case it will show
error

y=x.read(2)
print(y)
x.close()
Output:
Ra
Ram
Shyam

y=x.read(3)
print(y)
x.close()
Output:
Ram
Ram
Shyam

y=x.read(4)
print(y)
x.close()
Output:
Ram
Ram
Shyam

y=x.read(5)
print(y)
x.close()
Output:
Ram
S
Ram
Shyam

y=x.read(3)
print(y)
y=x.read(5)
print(y)
x.close() Output:
Ram
Shya
Ram
Shyam

x=open("Smahi.txt",“r
")
y=x.read(3)
Here data type of y
will be string

y=x.readline()
print(y)
x.close()
Output:
Ram
Ram
Shyam
Ajay

y=x.readline(2)
print(y)
x.close()
Output:
Ra
Ram
Shyam
Ajay

y=x.readline()
print(y)
y=x.readline()
print(y)
x.close()
Output:
Ram
Shyam
Ram
Shyam
Ajay

y=x.readline()
Here data type
of y is string

y=x.readlines()
print(y)
x.close()
Output:
['Ramn','Shyamn’,]
Ram
Shyam
Ajay

y=x.readlines()
print(y)
x.close()
Output:
['Ramn', 'Shyamn’, ‘Ajayn’]
Ram
Shyam
Ajay

y=x.readlines()
Here data type
of y is list

x=open("Smahi.txt")
for y in x:
print(y)
x.close()
output
Ram
Shyam
Ajay

x=open("Smahi.txt")
for y in x:
print(y)
x.close()
output
Here y is working Ram
like read or readline
Shyam
????????............ Ajay

x=open("Smahi.txt")
output
z=1 Ram
for y in x: 1
print(y) Shyam
print(z) 2
z=z+1 Ajay
x.close() 3
its working like
readline

Using “with” any
opened file can be
closed automatically
after accepting data
from the file no need
of using close( )

with open("Smahi.txt") as
x:
y=x.read()
print(y)
output
Ram
Shyam
Ajay

x:
y=x.read()
print(y[0])
output
R

x:
y=x.read()
print(type(y))
output
str

Using “with” while
writing in a file
with open(“Smahi.txt” , “w”) as x:
x.write(“Hello Sampurna”)

y=[ ]
a=int(input("Enter total number"))
for z in range(a):
y.append(input(“Number
")+"n")
x.writelines(y)
x.close()

x=open("Smahi.txt","r")
y=x.readlines()
m=0
z=0
while z<len(y):
print(int(y[z]),end=' ')
if int(y[z])>m:
m=int(y[z])
z=z+1
print("Largest number is ",m)
x.close()

y=x.readlines()
m=0
z=0
print("Entered number was n")
while z<len(y):
m=m+int(y[z])
z=z+1
print("nSum is ",m)
x.close()

y=x.readlines()
m,z=0,0
while z<len(y):
if int(y[z])%2==0:
m=m+1
z=z+1
print("Total even numbers are",
m)
x.close()

y=x.readlines()
m,z=0,0
while z<len(y):
if int(y[z])%2!=0:
m=m+1
z=z+1
print("Total odd numbers are", m)
x.close()

A binary file is a
computer file that is
not a text file. The
term “binary file” is
often used as a term
meaning
“Non text file”

Generally a binary
file is created to store
list, tuples,
dictionaries and
nested list.

In Binary files 1st the
data are serialized
and then stored.

Serialization is the
process in which the list,
tuples and the
dictionaries are
converted into byte
stream and then stored in
the file

Pickling converts an
object in byte stream in
such a way that it can be
reconstructed in original
form when un - pickled or
de - serialized

In order to work with
pickle module, we
must 1st import it
using syntax
import pickle

In pickle module there
are two functions
dump() and load(), 1st
one is used to store the
data in file and the 2nd
is used to access data
from the file

Storing data in binary file
import pickle
emp1={'name':"amit", "age":23}
emp2={'name':"sumit", "age":38}
emp3={'name':"ajay", "age":18}
em=open("emp.dat","wb")
pickle.dump(emp1,em)
print("Data dumped-written in file....
")
em.close()

Accessing data from binary file
import pickle
emp={}
em=open("emp.dat","rb")
try:
while True:
emp=pickle.load(em)
print(emp)
except EOFError:
em.close()

Accessing data from binary file
import pickle
emp={}
print("Name Age")
try:
while True:
emp=pickle.load(em)
print(emp['name'],'t',emp['age'])
except EOFError:
em.close()

Accessing selected data from binary file
import pickle
emp={ }
m=0
print("Name Age")
try:
while True:
emp=pickle.load(em)
if emp['age']>m:
m=emp['age']
n=emp['name']
except EOFError:
em.close()
print(n, m)

Let the content of the file Smahi.txt is : -
Ram
Shyam
Ajay
Manoj
Rajeev
x=open("Smahi.txt")
y=x.tell()
print(y) Output
0

Ram
Shyam
Ajay
Manoj
Rajeev
x=open("Smahi.txt") Output
y=x.tell()
print(y) 0
z=x.read(2)
y=x.tell()
print(y) 2

: -
Ram
Shyam
Ajay
Manoj
Rajeev
x=open("Smahi.txt")
z=x.read()
y=x.tell()
OUTPUT
print(y) 33

: -
Ram
Shyam
Ajay
Manoj
Rajeev
x=open("Smahi.txt")
z=x.readline()
y=x.tell()
OUTPUT
print(y) 5

Let the content of the file Smahi.txt is :
-
Ram
Shyam
Ajay
Manoj
Rajeev
x=open("Smahi.txt")
z=x.readline()
z=x.readline()
y=x.tell() OUTPUT
print(y) 12

-
Ram
Shyam
Ajay
Manoj
Rajeev
x=open("Smahi.txt") OUTPUT
y=x.tell() 0
print(y) 2
x.seek(2)
y=x.tell()
print(y)

-
Ram
Shyam
Ajay
x=open("Smahi.txt") Manoj
y=x.tell() Rajeev
print(y)
x.seek(12) OUTPUT
z=x.read(5) 0
print(z) Ajay
y=x.tell()
print(y) 18

Let the content of the Ram
file Smahi.txt is : - Shyam
Ajay
y=x.tell() OUTPUT Rajeev
print(y) 0
x.seek(12)
z=x.read(6)
print(z) Ajay
y=x.tell()
print(y) 19

-
Ram
Shyam
Ajay
y=x.tell() Rajeev
print(y)
m=x.read(8) OUTPUT
print(m) ERROR
x.seek(-5) indexing is
y=x.tell() always
print(y) positive

-
Ram
x=open("Smahi.txt") Shyam
x.seek(12) Ajay
print(x.tell()) Manoj
x.seek(-5,2) Rajeev
print(x.tell())
x.close()
Error: - Cursor movement is allowed
from beginning of the file only. Then
how to move the cursor from any
where ?????

Open the
text file in
binary mode

-
Ram
x=open("Smahi.txt", "rb") Shyam
x.seek(12) Ajay
print(x.tell()) Manoj
x.seek(-5,2) Rajeev
print(x.tell())
x.close()
Okay: - Cursor movement is allowed
from any where in “BINARY FILE”

-
Ram
em=open("Smahi.txt","rb") Shyam
z=em.read() Ajay
print(em.tell()) Manoj
em.seek(0,2) Rajeev
print(em.tell())
em.close() OUTPUT
33
33

0 moves from beginning
1 moves from current
position
2 moves from end

“END” Ram
em=open("Smahi.txt","rb")
Shyam
em.seek(0,2) Ajay
em.seek(4,2) Rajeev
print(em.tell())
em.seek(-4,2)
print(em.tell())
OUTPUT
em.close() 33
37
29

Shyam
em.seek(0,1) Ajay
em.seek(14,1)
Rajeev
print(em.tell())
OUTPUT
em.seek(-4,1) 0
print(em.tell()) 14
em.seek(3,1) 10
print(em.tell()) 13
em.close()

Shyam
em.seek(0,0) Ajay
em.seek(14,0)
Rajeev
print(em.tell())
em.seek(-4,0)
print(em.tell())
OUTPUT
em.close() 0
14
Error

“Start” Ram
em=open(“Smahi.txt","rb+")
Shyam
em.seek(100,0) Ajay
em.close() Rajeev
OUTPUT
100
Here size of the file is 33 bytes, but if
we want to move beyond the limit, its
allowed but the size of the file does
not changes.

Ram
em=open(“Smahi.txt","rb+")Shyam
x=em.read() Ajay
em.seek(100,0) Rajeev
print(em.tell()) OUTPUT
em.seek(0,0) 33
print(em.tell()) 100
y=em.read() 0
print(len(x)) 33
print(len(y)) 33
em.close() BUT……….

If we move the file
pointer beyond the
limit and tried to write
anything, REMEMBER
the same will be written
at that point and the
size of the file will
expand.

em.seek(0,2)
OUTPUT
print(em.tell()) 33
em.seek(100,0)
em.seek(0,2)
print(em.tell()) 33
em.close()

em.seek(0,2) OUTPUT
print(em.tell()) 33
em.seek(100,0)
em.write(b"Ramu")
em.seek(0,2)
em.close()

Seek and Tell on Binary files
import pickle
emp={ }
print(em.tell())
try:
while True:
OUTPUT
emp=pickle.load(em) 0
print(em.tell()) 42
except EOFError: 85
em.close() 127

import pickle
emp={}
bmp=[]
em=open("emp.dat",'rb')
try:
while True:
emp=pickle.load(em)
bmp.append(em.tell())
except EOFError:
em.close()
print(bmp) [42, 85,
127]

import pickle z=0
emp={} em=open("emp.dat",'rb')
bmp=[] emp=pickle.load(em)
em=open("emp.dat",'rb') print(emp)
try: while z<len(bmp)-1:
while True:
em.seek(bmp[z])
emp=pickle.load(em)
emp=pickle.load(em)
bmp.append(em.tell()) print(emp)
except EOFError: z=z+1
em.close() em.close()

Modifying the contents of a binary file
import pickle
x=input("Please enter name to be modified ")
y=open("emp.dat","rb+")
a={ }
try:
while True:
z=y.tell()
a=pickle.load(y)
if a['name']==x:
print(a['name'],' ',a['age'])
a['age']+=5
y.seek(z)
pickle.dump(a,y)
except EOFError:
y.close()

1)
import pickle
a={}
try:
while True:
a=pickle.load(y)
except EOFError:
y.close()
continued ………… go to next
slide

Modifying the contents of a binary file (Page 2)
x=input("nnPlease enter name to be modified ")
a={ }
k=0
try:
while True:
z=y.tell()
a=pickle.load(y)
if a['name']==x:
print("Name found ")
a['age']=int(input("Enter new age "))
y.seek(z)
pickle.dump(a,y)
k=1
except EOFError:
y.close()
if k==0:
print("Sorry ",x," not found ") continued ……… go to next
slide

Modifying the contents of a binary file (Page 3)
a={}
try:
while True:
a=pickle.load(y)
except EOFError:
y.close()

emp={}
em=open("emp.dat","ab")
x=1
while x==1:
emp['name']=input("Please enter name
")
emp['age']=int(input("Please enter age
"))
pickle.dump(emp,em)
x=int(input("Please enter 1 to continue
"))
print("Data dumped-written in file.... ")
em.close()

Deleting records from a binary file (Slide
1)
import os
import pickle
a={}
try:
while True:
a=pickle.load(y)
except EOFError:
y.close()
Continued………... Goto Next
Slide

Deleting records from a binary file (Slide 2)
x=input("nnEnter name to be deleted ")
z=open("bmp.dat","wb+")
a={}
b=0
try:
while True:
a=pickle.load(y)
if a['name']!=x:
pickle.dump(a,z)
else:
b=1
except EOFError:
y.close()
z.close()
if b==1:
print("Data found, and deleted ")
else:
print("Deletion not possible ")
os.remove("emp.dat")
os.rename("bmp.dat","emp.dat") Continued………...
Goto Next Slide

Deleting records from a binary file (Slide
3)
a={}
try:
while True:
a=pickle.load(y)
except EOFError:
y.close()

def enter():
import pickle
emp={}
em=open("stud.dat","wb")
x=1
for xx in range(25):
print("n")
emp['name']=input("Please enter name ")
emp['roll']=int(input("Please enter roll "))
emp['marks']=int(input("Please enter marks
"))
pickle.dump(emp,em)
em.close()

def display():
import pickle
emp={}
em=open("stud.dat","rb+")
print("n")
print("Name roll marks")
try:
while True:
emp=pickle.load(em)
print(emp['name'],emp['roll'],emp['marks'])
except EOFError:
em.close()

def modify():
import pickle
print("n")
x=input("Please enter name to be modified ")
y=open("stud.dat","rb+")
a={}
try:
while True:
z=y.tell()
a=pickle.load(y)
if a['name']==x:
print("Data found ")
print(a['name'],' ',a['marks'], ' ',a['roll'])
print(".......and modified ")
a['marks']+=5
y.seek(z)
pickle.dump(a,y)
except EOFError:
y.close()

def adding():
import pickle
emp={}
em=open("stud.dat","ab")
x=1
print("n")
emp['name']=input("Please enter name ")
emp['roll']=int(input("Please enter roll "))
emp['marks']=int(input("Please enter marks
"))
pickle.dump(emp,em)
em.close()

ch='y'
while ch=='y':
x=int(input("Enter
n1..overwriten2..appendn3..displayn4..modify
marksn5..exit from a file "))
if x==1:
enter()
if x==2:
adding()
if x==3:
display()
if x==4:
modify()
if x==5:
break
ch=input("Press y to continue ")

Creating csv files
import csv
x=open("abc.csv","w"
)
x.close()

Creating csv files
import csv
x=open("abc.csv","w")
y=csv.writer(x)
z=(1,"amit",10)
y.writerow(z)
x.close()

Creating csv files
import csv
y=csv.writer(x)
z=(1,"amit",10)
y.writerow(z)
z=(2,"sumit",11)
y.writerow(z)
z=(3,"ajay",12)
y.writerow(z)
z=(4,"sanjay",13)
y.writerow(z)
x.close()

Creating csv files
import csv
y=csv.writer(x)
z=[1,"amit",10]
y.writerow(z)
z=[2,"sumit",11]
y.writerow(z)
z=[3,"ajay",12]
y.writerow(z)
z=[4,"sanjay",13]
y.writerow(z)
x.close()

Creating csv files
import csv
y=csv.writer(x)
z=[1,"amit",10]
y.writerow(z)
z=(2,"sumit",11)
y.writerow(z)
z=[3,"ajay",12]
y.writerow(z)
z=(4,"sanjay",13)
y.writerow(z)
x.close()

Creating csv files
import csv
y=csv.writer(x)
y.writerow(["Roll","Name","Marks"])
z=[1,"amit",10]
y.writerow(z)
z=(2,"sumit",11)
y.writerow(z)
z=[3,"ajay",12]
y.writerow(z)
z=(4,"sanjay",13)
y.writerow(z)
x.close()

Creating csv files
import csv
y=csv.writer(x)
for m in range(5):
r=int(input("Roll Please "))
n=input("Name Please ")
m=int(input("Marks Please "))
y.writerow([r,n,m])
x.close()

Creating csv files
import csv
y=csv.writer(x)
LIST=[]
for m in range(3):
r=int(input("Roll Please "))
n=input("Name Please ")
m=int(input("Marks Please "))
LIST.append([r,n,m])
y.writerows(LIST)
x.close()

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