Class XII Computer Science Board Preparation

kb=float(input("Enter KB: "))
print("Bytes:",kb*1024)
print("MB:",kb/1024)
print("GB:",kb/1024**2)

units=["Byte","KB","MB","GB","TB","PB"]
for i,u in enumerate(units):
    print(f"{u} = 2^{10*i} bytes = {2**(10*i):,}")

acc=0
for val in [10,20,30,40]:
    acc+=val
    print(f"ACC after adding {val}: {acc}")

cpu="Intel i5"
ram="8 GB"
hdd="512 GB SSD"
print(f"CPU: {cpu}\nRAM: {ram}\nStorage: {hdd}")

b=int(input("Bytes: "))
print(f"KB: {b/1024:.2f}\nMB: {b/1024**2:.4f}\nGB: {b/1024**3:.6f}")

instructions=["FETCH","DECODE","EXECUTE","STORE"]
for step in instructions:
    print(f"→ {step}")

modules=[4,8,4]
print("Total RAM:",sum(modules),"GB =",sum(modules)*1024**3,"bytes")

buses={"Address bus":32,"Data bus":64,"Control bus":8}
for b,w in buses.items():
    print(f"{b}: {w}-bit ({2**w:,} combinations)")

cache=[]
for addr in [100,200,100,300,200,100,400]:
    if addr in cache:
        print(f"{addr}: HIT")
    else:
        cache.append(addr)
        if len(cache)>3: cache.pop(0)
        print(f"{addr}: MISS")

a=int(input("Size A in MB: "))
b=int(input("Size B in MB: "))
if a>b: print("A is larger")
elif b>a: print("B is larger")
else: print("Equal")

types={"OS":"System","Driver":"System","Word":"Application","Compiler":"System Tool"}
name=input("Enter software name: ")
print(types.get(name,"Unknown type"))

statements=["print(1+2)","print('Hello')","print(2**8)"]
for s in statements:
    print(f"Executing: {s}")
    exec(s)

data={"System":["OS","Driver","BIOS"],"Application":["Word","Excel","VLC"],"Utility":["Antivirus","Zip","Defrag"]}
for cat,exs in data.items():
    print(f"{cat}: {', '.join(exs)}")

sw={"Windows":"System","Photoshop":"Application","BIOS":"System","Chrome":"Application"}
for s,t in sw.items():
    print(f"{s} → {t}")

rows=[("Translation","Entire program","Line by line"),("Speed","Faster","Slower"),("Error report","After full scan","At first error")]
print(f"{"Feature":20} {"Compiler":15} {"Interpreter":15}")
for r in rows:
    print(f"{r[0]:20} {r[1]:15} {r[2]:15}")

files=["app.exe","driver.sys","notes.docx","game.dll"]
exts={"exe":"Application","sys":"System","dll":"System Library","docx":"Document"}
for f in files:
    ext=f.split(".")[-1]
    print(f"{f} → {exts.get(ext,"Unknown")}")

valid_keys=["ABC123","XYZ789","PRO456"]
key=input("Enter license key: ")
if key in valid_keys:
    print("License valid. Software activated.")
else:
    print("Invalid key. Please purchase.")

sw=[("OS","system"),("Word","app"),("Driver","system"),("Excel","app"),("BIOS","system")]
sys=sum(1 for _,t in sw if t=="system")
app=sum(1 for _,t in sw if t=="app")
print(f"System: {sys}, Application: {app}")

software={"name":"CBSEMOCK Suite","version":"2.5.1","type":"Application","license":"Freeware"}
for k,v in software.items():
    print(f"{k.capitalize():12}: {v}")

import time
code=[f"x={i}*{i}" for i in range(1000)]
t=time.time()
for line in code: exec(line)
print(f"Interpreted: {(time.time()-t)*1000:.2f} ms for {len(code)} lines")

ip=input("Enter IP: ")
parts=ip.split(".")
if len(parts)==4 and all(p.isdigit() and 0<=int(p)<=255 for p in parts):
    print("Valid IPv4")
else:
    print("Invalid IPv4")

packet={"src":"192.168.1.1","dst":"10.0.0.1","port":80,"data":"GET /index.html"}
for k,v in packet.items():
    print(f"{k.upper():8}: {v}")

url=input("URL: ")
if url.startswith("https"): print("Secure (HTTPS)")
elif url.startswith("http"): print("Not secure (HTTP)")
else: print("Unknown protocol")

protocols={"HTTP":80,"HTTPS":443,"FTP":21,"SSH":22,"SMTP":25,"DNS":53}
for p,port in protocols.items():
    print(f"{p:8}: Port {port}")

blocked=["192.168.1.100","10.0.0.5"]
requests=["192.168.1.1","192.168.1.100","172.16.0.1","10.0.0.5"]
for ip in requests:
    status="BLOCKED" if ip in blocked else "ALLOWED"
    print(f"{ip:16} → {status}")

size_mb=float(input("File size in MB: "))
bw_mbps=float(input("Bandwidth in Mbps: "))
time_sec=(size_mb*8)/bw_mbps
print(f"Transfer time: {time_sec:.2f} seconds")

phishing=["urgent","verify","account suspended","click now","password"]
subject=input("Email subject: ").lower()
if any(w in subject for w in phishing):
    print("⚠ Possible phishing email!")
else:
    print("Looks safe.")

devices=["PC1","PC2","Laptop1","Printer"]
print("Star Topology:")
print("Hub")
for d in devices:
    print(f"  └─ {d}")

import random
packets=[(random.randint(1,3),random.randint(1,3)) for _ in range(10)]
sent=received=lost=0
for s,r in packets:
    sent+=s
    received+=r
    if s!=r: lost+=abs(s-r)
print(f"Sent:{sent} Received:{received} Lost:{lost}")

open_ports=[80,443,22,3306]
for port in range(20,90):
    status="OPEN" if port in open_ports else "closed"
    if status=="OPEN":
        print(f"Port {port}: {status}")

n=int(input("Decimal: "))
b=""
while n>0:
    b=str(n%2)+b
    n//=2
print("Binary:",b or "0")

n=int(input("Decimal: "))
o=""
while n>0:
    o=str(n%8)+o
    n//=8
print("Octal:",o or "0")

n=int(input("Decimal: "))
h="0123456789ABCDEF"
s=""
while n>0:
    s=h[n%16]+s
    n//=16
print("Hex:",s or "0")

b=input("Binary: ")
d=0
for bit in b:
    d=d*2+int(bit)
print("Decimal:",d)

n=int(input("Enter decimal: "))
print(f"Binary : {bin(n)[2:]}")
print(f"Octal  : {oct(n)[2:]}")
print(f"Hex    : {hex(n)[2:].upper()}")

a=input("Binary 1: ")
b=input("Binary 2: ")
result=bin(int(a,2)+int(b,2))[2:]
print("Sum:",result)

b=input("Binary: ")
comp="".join("1" if c=="0" else "0" for c in b)
print("1's complement:",comp)

b=input("Binary: ")
ones="".join("1" if c=="0" else "0" for c in b)
two=bin(int(ones,2)+1)[2:]
print("2's complement:",two.zfill(len(b)))

h=input("Hex: ")
d=int(h,16)
b=bin(d)[2:]
print(f"Hex {h} = Binary {b}")

print(f"{"Dec":4} {"Bin":8} {"Oct":4} {"Hex":4}")
for i in range(16):
    print(f"{i:4} {bin(i)[2:]:>8} {oct(i)[2:]:4} {hex(i)[2:].upper():4}")

print("A B AND OR NOT-A")
for a in [0,1]:
    for b in [0,1]:
        print(f"{a} {b}  {a&b}   {a|b}   {1-a}")

print("A B XOR XNOR")
for a in [0,1]:
    for b in [0,1]:
        xor=a^b
        print(f"{a} {b}  {xor}    {1-xor}")

def nand(a,b): return int(not(a and b))
def nor(a,b): return int(not(a or b))
for a in [0,1]:
    for b in [0,1]:
        print(f"A={a},B={b}: NAND={nand(a,b)}, NOR={nor(a,b)}")

print("A B (A+B)' A'·B' Match? (A·B)' A'+B' Match?")
for a in [0,1]:
    for b in [0,1]:
        lhs1=int(not(a or b))
        rhs1=(1-a)&(1-b)
        lhs2=int(not(a and b))
        rhs2=(1-a)|(1-b)
        print(f"{a} {b}    {lhs1}       {rhs1}       {lhs1==rhs1}    {lhs2}        {rhs2}       {lhs2==rhs2}")

def half_adder(a,b):
    s=a^b  # XOR
    c=a&b  # AND
    return s,c
print("A B | Sum Carry")
for a in [0,1]:
    for b in [0,1]:
        s,c=half_adder(a,b)
        print(f"{a} {b} |  {s}    {c}")

def F(a,b,c): return (not a and b) or (a and not b and c)
minterms=[]
for a in [0,1]:
    for b in [0,1]:
        for c in [0,1]:
            if F(a,b,c): minterms.append(4*a+2*b+c)
print("Minterms:",minterms)

def half_add(a,b): return a^b,a&b
def full_add(a,b,cin):
    s1,c1=half_add(a,b)
    s2,c2=half_add(s1,cin)
    return s2,c1|c2
print("A B Cin Sum Cout")
for a in [0,1]:
    for b in [0,1]:
        for c in [0,1]:
            s,co=full_add(a,b,c)
            print(f"{a} {b}  {c}   {s}   {co}")

print("A B | A+AB | A | Equal?")
for a in [0,1]:
    for b in [0,1]:
        lhs=a|(a&b)
        print(f"{a} {b} |   {lhs}   | {a} | {lhs==a}")

A,B,C=1,0,1
expr="A and not B or C"
result=eval(expr)
print(f"A={A},B={B},C={C}: {expr} = {int(result)}") 

def mux2to1(a,b,s):
    return (a and not s) or (b and s)
print("A B S | Out")
for a in [0,1]:
    for b in [0,1]:
        for s in [0,1]:
            print(f"{a} {b} {s} |  {int(mux2to1(a,b,s))}")

arr=[64,34,25,12,22,11,90]
n=len(arr)
for i in range(n-1):
    for j in range(n-i-1):
        if arr[j]>arr[j+1]:
            arr[j],arr[j+1]=arr[j+1],arr[j]
    print(f"Pass {i+1}: {arr}")

arr=[10,25,3,47,8,15]
key=int(input("Search: "))
for i,v in enumerate(arr):
    print(f"Checking index {i}: {v}")
    if v==key:
        print(f"Found at index {i}")
        break
else:
    print("Not found")

arr=sorted([10,25,3,47,8,15,55,2])
key=int(input("Search: "))
lo,hi=0,len(arr)-1
while lo<=hi:
    mid=(lo+hi)//2
    print(f"Checking mid={mid}: {arr[mid]}")
    if arr[mid]==key: print("Found!"); break
    elif key<arr[mid]: hi=mid-1
    else: lo=mid+1
else: print("Not found")

arr=[3,1,4,1,5,9,2,6]
max_v=min_v=arr[0]
for x in arr[1:]:
    if x>max_v: max_v=x
    if x<min_v: min_v=x
print(f"Max:{max_v} Min:{min_v}")

import math
arr=list(range(1,101))
key=int(input("Search (1-100): "))
linear_steps=next(i+1 for i,v in enumerate(arr) if v==key)
binary_steps=math.floor(math.log2(len(arr)))+1
print(f"Linear steps: {linear_steps}\nBinary max steps: {binary_steps}")

arr=[12,11,13,5,6]
for i in range(1,len(arr)):
    key=arr[i]
    j=i-1
    while j>=0 and arr[j]>key:
        arr[j+1]=arr[j]
        j-=1
    arr[j+1]=key
    print(f"Step {i}: {arr}")

arr=[64,25,12,22,11]
for i in range(len(arr)):
    min_idx=i
    for j in range(i+1,len(arr)):
        if arr[j]<arr[min_idx]: min_idx=j
    arr[i],arr[min_idx]=arr[min_idx],arr[i]
    print(f"Step {i+1}: {arr}")

arr=[1,2,3,5,4]
is_sorted=all(arr[i]<=arr[i+1] for i in range(len(arr)-1))
print("Sorted" if is_sorted else "Not sorted")

arr=[10,5,8,20,3,15]
uniq=sorted(set(arr),reverse=True)
print("Second largest:",uniq[1] if len(uniq)>1 else "N/A")

arr=[5,1,4,2,8]
comparisons=0
n=len(arr)
for i in range(n-1):
    for j in range(n-i-1):
        comparisons+=1
        if arr[j]>arr[j+1]: arr[j],arr[j+1]=arr[j+1],arr[j]
print(f"Sorted: {arr}\nComparisons: {comparisons}")

a=int(input("a: "))
b=int(input("b: "))
a,b=b,a
print(f"a={a}, b={b}")

y=int(input("Year: "))
if (y%4==0 and y%100!=0) or y%400==0:
    print("Leap year")
else:
    print("Not a leap year")

n=int(input("Terms: "))
a,b=0,1
for _ in range(n):
    print(a,end=" ")
    a,b=b,a+b

def gcd(a,b):
    while b: a,b=b,a%b
    return a
a=int(input("a: "))
b=int(input("b: "))
print("GCD:",gcd(a,b))

s=input("String: ")
if s==s[::-1]:
    print("Palindrome")
else:
    print("Not a palindrome")

p=float(input("Principal: "))
r=float(input("Rate%: "))
t=float(input("Time(yrs): "))
si=p*r*t/100
ci=p*(1+r/100)**t-p
print(f"SI: {si:.2f}  CI: {ci:.2f}")

n=int(input("Table of: "))
for i in range(1,11):
    print(f"{n} x {i:2} = {n*i:3}")

s=input("String: ").lower()
vowels="aeiou"
v=sum(1 for c in s if c in vowels)
k=sum(1 for c in s if c.isalpha() and c not in vowels)
print(f"Vowels:{v} Consonants:{k}")

n=int(input("N: "))
sieve=[True]*(n+1)
sieve[0]=sieve[1]=False
for i in range(2,int(n**0.5)+1):
    if sieve[i]:
        for j in range(i*i,n+1,i): sieve[j]=False
print([i for i in range(n+1) if sieve[i]])

a=float(input("a: "))
op=input("Operator: ")
b=float(input("b: "))
if op=="+": print(a+b)
elif op=="-": print(a-b)
elif op=="*": print(a*b)
elif op=="/" and b!=0: print(a/b)
else: print("Invalid")

a,b=int(input("a: ")),int(input("b: "))
print(f"+ {a+b}\n- {a-b}\n* {a*b}\n/ {a/b:.2f}\n// {a//b}\n% {a%b}\n** {a**b}")

expr1=2+3*4-1
expr2=(2+3)*(4-1)
expr3=2+(3*(4-1))
print(f"2+3*4-1 = {expr1}")
print(f"(2+3)*(4-1) = {expr2}")
print(f"2+(3*(4-1)) = {expr3}")

a,b=5,3
for op,res in [("==",a==b),(">",a>b),("<",a<b),(">=",a>=b),("<=",a<=b),("!=",a!=b)]:
    print(f"{a} {op} {b} = {res}")

for a in [True,False]:
    for b in [True,False]:
        print(f"{str(a):5} AND {str(b):5} = {a and b}; OR = {a or b}; NOT a = {not a}")

a,b=12,10
print(f"a={a} ({bin(a)})  b={b} ({bin(b)})")
print(f"AND: {a&b} ({bin(a&b)})")
print(f"OR:  {a|b} ({bin(a|b)})")
print(f"XOR: {a^b} ({bin(a^b)})")
print(f"NOT: {~a}")
print(f"<<1: {a<<1}  >>1: {a>>1}")

x=10
for op,val in [("+",3),("-",2),("*",4),("//",5),("%",3),("**",2)]:
    old=x
    if op=="+": x+=val
    elif op=="-": x-=val
    elif op=="*": x*=val
    elif op=="//": x//=val
    elif op=="%": x%=val
    elif op=="**": x**=val
    print(f"x{op}={val}: {old} → {x}")

lst=[1,2,3,4]
tup=(10,20,30)
s="Hello Python"
print(3 in lst, 5 not in lst)
print(20 in tup, 40 not in tup)
print("Python" in s, "Java" not in s)

a=[1,2,3]
b=a
c=[1,2,3]
print("b=a, so a is b:",a is b)
print("c=[1,2,3], a is c:",a is c)
print("a == c:",a==c)

a,b,c=10,3,True
result=((a+b*2)//5 >= 3) and c or (a%b != 0)
print(f"((10+3*2)//5 >= 3) and True or (10%3 != 0) = {result}")

expr="4 + 8 * (6 - 2) ** 2 / 16"
print(f"Expression: {expr}")
print(f"Step1: 6-2 = 4")
print(f"Step2: 4**2 = 16")
print(f"Step3: 8*16 = 128")
print(f"Step4: 128/16 = 8.0")
print(f"Step5: 4+8.0 = 12.0")
print(f"Result: {eval(expr)}")

for n in range(2,51):
    for i in range(2,int(n**0.5)+1):
        if n%i==0: break
    else:
        print(n,end=" ")

for i in range(1,6):
    print("*"*i)

n=int(input("Number: "))
print(sum(int(d) for d in str(abs(n))))

print("  "*2,end="")
for j in range(1,6): print(f"{j:4}",end="")
print()
for i in range(1,6):
    print(f"{i:2}|",end="")
    for j in range(1,6):
        print(f"{i*j:4}",end="")
    print()

for n in range(1,1001):
    digits=str(n)
    p=len(digits)
    if sum(int(d)**p for d in digits)==n:
        print(n,end=" ")

n=5
for i in range(1,n+1):
    print(" "*(n-i)+"*"*(2*i-1))
for i in range(n-1,0,-1):
    print(" "*(n-i)+"*"*(2*i-1))

n=input("Number: ")
for d in "0123456789":
    c=n.count(d)
    if c: print(f"Digit {d}: {c} time(s)")

n=5
num=1
for i in range(1,n+1):
    for j in range(i):
        print(num,end=" ")
        num+=1
    print()

import random
secret=random.randint(1,10)
guess=0
attempts=0
while guess!=secret:
    guess=int(input("Guess (1-10): "))
    attempts+=1
    if guess<secret: print("Too low")
    elif guess>secret: print("Too high")
print(f"Correct in {attempts} attempts!")

for i in range(1,6):
    print(*range(1,i+1))

s=input("String: ")
v=sum(1 for c in s if c.lower() in "aeiou")
k=sum(1 for c in s if c.isalpha() and c.lower() not in "aeiou")
d=sum(1 for c in s if c.isdigit())
sp=s.count(" ")
print(f"Vowels:{v} Consonants:{k} Digits:{d} Spaces:{sp}")

s=input("Sentence: ")
result=" ".join(w[::-1] for w in s.split())
print(result)

a=input("String 1: ").lower().replace(" ","")
b=input("String 2: ").lower().replace(" ","")
print("Anagram" if sorted(a)==sorted(b) else "Not anagram")

s=input("String: ").replace(" ","")
freq={c:s.count(c) for c in set(s)}
max_c=max(freq,key=freq.get)
print(f"Most frequent: {max_c} ({freq[max_c]} times)")

s=input("String: ")
seen=set()
result="".join(c for c in s if c not in seen and not seen.add(c))
print(result)

msg=input("Message: ").lower()
shift=int(input("Shift: "))
result="".join(chr((ord(c)-97+shift)%26+97) if c.isalpha() else c for c in msg)
print("Encrypted:",result)

s=input("Text: ")
words=s.split()
sentences=s.count(".")+s.count("!")+s.count("?")
avg=sum(len(w.strip(".,!?")) for w in words)/len(words) if words else 0
print(f"Words:{len(words)} Sentences:{sentences} Avg length:{avg:.1f}")

import re
s=input("String: ")
nums=re.findall(r"\d+",s)
print("Numbers found:",[int(n) for n in nums])

s=input("String: ")
result=" ".join(w[0].upper()+w[1:].lower() if w else "" for w in s.split())
print(result)

import re
pwd=input("Password: ")
score=0
if len(pwd)>=8: score+=1
if re.search(r"[A-Z]",pwd): score+=1
if re.search(r"[a-z]",pwd): score+=1
if re.search(r"\d",pwd): score+=1
if re.search(r"[!@#$%]",pwd): score+=1
strength=["Very Weak","Weak","Fair","Strong","Very Strong","Excellent"][score]
print(f"Strength: {strength} ({score}/5)")

lst=list(map(int,input("Numbers: ").split()))
max1=max2=float("-inf")
for x in lst:
    if x>max1: max2=max1;max1=x
    elif x>max2: max2=x
print("2nd largest:",max2)

lst=list(map(int,input("Numbers: ").split()))
seen=set()
result=[x for x in lst if x not in seen and not seen.add(x)]
print(result)

matrix=[[1,2,3],[4,5,6],[7,8,9]]
flat=[x for row in matrix for x in row]
print(flat)

lst=[1,2,3,4,5]
k=int(input("Rotate by: "))%len(lst)
print(lst[k:]+lst[:k])

a=list(map(int,input("List A: ").split()))
b=list(map(int,input("List B: ").split()))
print("Union:",list(set(a)|set(b)))
print("Intersection:",list(set(a)&set(b)))

A=[[1,2],[3,4]]
B=[[5,6],[7,8]]
C=[[sum(A[i][k]*B[k][j] for k in range(2)) for j in range(2)] for i in range(2)]
for row in C: print(row)

words=input("Words: ").split()
words.sort(key=len)
print(words)

lst=[1,2,3,4,5,6,7,8]
target=int(input("Target sum: "))
pairs=[(lst[i],lst[j]) for i in range(len(lst)) for j in range(i+1,len(lst)) if lst[i]+lst[j]==target]
print("Pairs:",pairs)

lst=list(range(1,11))
n=int(input("Chunk size: "))
chunks=[lst[i:i+n] for i in range(0,len(lst),n)]
print(chunks)

matrix=[[1,2,3],[4,5,6],[7,8,9]]
transposed=[[matrix[j][i] for j in range(3)] for i in range(3)]
for row in transposed: print(row)

t=tuple(x**2 for x in range(1,11))
print(t)

t=(1,2,3,2,4,2,5,1,1)
max_elem=max(set(t),key=t.count)
print(f"{max_elem} appears {t.count(max_elem)} times")

data=[("name","Alice"),("age",16),("grade","A")]
d=dict(data)
print(d)

def stats(lst):
    return min(lst),max(lst),sum(lst)/len(lst)
data=[10,25,3,47,8,15]
mi,mx,av=stats(data)
print(f"Min:{mi} Max:{mx} Avg:{av:.1f}")

keys=("name","age","city")
vals=("Alice",16,"Durgapur")
for k,v in zip(keys,vals):
    print(f"{k}: {v}")

data=[(3,"banana"),(1,"apple"),(2,"cherry")]
data.sort(key=lambda x:x[1])
for item in data:
    print(item)

t=((1,2),(3,4),(5,6))
for a,b in t:
    print(f"{a}+{b}={a+b}")

t1=(1,2,3,4,5)
t2=(3,4,5,6,7)
common=tuple(set(t1)&set(t2))
print("Common:",common)

n=int(input("How many numbers: "))
t=tuple(int(input(f"Number {i+1}: ")) for i in range(n))
print("Tuple:",t)
print("Sum:",sum(t))

a=int(input("a: "))
b=int(input("b: "))
print(f"Before: a={a}, b={b}")
a,b=b,a
print(f"After:  a={a}, b={b}")

text=input("Enter text: ").lower()
freq={}
for w in text.split():
    freq[w]=freq.get(w,0)+1
for k,v in sorted(freq.items(),key=lambda x:-x[1]):
    print(f"{k}: {v}")

d={"a":1,"b":2,"c":3}
inverted={v:k for k,v in d.items()}
print(inverted)

students={"Alice":{"Math":90,"Sci":85},"Bob":{"Math":72,"Sci":68}}
for name,marks in students.items():
    avg=sum(marks.values())/len(marks)
    print(f"{name}: Avg={avg:.1f} Grade={"A" if avg>=80 else "B"}")

words=["apple","ant","ball","cat","cherry","banana"]
groups={}
for w in words:
    key=w[0]
    groups.setdefault(key,[]).append(w)
for k,v in sorted(groups.items()):
    print(f"{k}: {v}")

d1={"a":1,"b":2,"c":3}
d2={"b":10,"c":20,"d":30}
merged={**d1}
for k,v in d2.items():
    merged[k]=merged.get(k,0)+v
print(merged)

book={}
while True:
    cmd=input("add/search/quit: ")
    if cmd=="add":
        n=input("Name: ");p=input("Phone: ");book[n]=p
    elif cmd=="search":
        n=input("Name: ");print(book.get(n,"Not found"))
    elif cmd=="quit": break
print("Contacts:",len(book))

s=input("String: ")
freq={}
for c in s:
    freq[c]=freq.get(c,0)+1
for k,v in sorted(freq.items()):
    print(f"{repr(k)}: {v}")

d1={"a":1,"b":2,"c":3,"d":4}
d2={"b":20,"c":30,"e":50}
common=set(d1)&set(d2)
for k in common:
    print(f"Key {k}: d1={d1[k]}, d2={d2[k]}")

d={"banana":3,"apple":1,"cherry":2}
for k,v in sorted(d.items(),key=lambda x:x[1]):
    print(f"{k}: {v}")

inv={"Pen":{"qty":100,"price":5},"Book":{"qty":50,"price":80}}
for item,info in inv.items():
    total=info["qty"]*info["price"]
    print(f"{item:10} Qty:{info["qty"]:5} Price:{info["price"]:6} Total:{total:7}")

def factorial(n):
    if n==0 or n==1: return 1
    return n*factorial(n-1)
n=int(input("N: "))
print(f"{n}! = {factorial(n)}")

def stats(*nums):
    return min(nums),max(nums),sum(nums)/len(nums)
result=stats(10,25,3,47,8,15)
print(f"Min:{result[0]} Max:{result[1]} Avg:{result[2]:.1f}")

def bsearch(arr,key,lo,hi):
    if lo>hi: return -1
    mid=(lo+hi)//2
    if arr[mid]==key: return mid
    elif key<arr[mid]: return bsearch(arr,key,lo,mid-1)
    else: return bsearch(arr,key,mid+1,hi)
arr=sorted([10,25,3,47,8,15,55,2])
key=int(input("Search: "))
print("Found at index:",bsearch(arr,key,0,len(arr)-1))

def logger(fn):
    def wrapper(*args,**kwargs):
        print(f"Calling {fn.__name__} with {args}")
        result=fn(*args,**kwargs)
        print(f"Result: {result}")
        return result
    return wrapper
@logger
def add(a,b): return a+b
add(3,4)

def make_multiplier(n):
    def multiply(x):
        return x*n
    return multiply
double=make_multiplier(2)
triple=make_multiplier(3)
print(double(5), triple(5))

def hanoi(n,src,dst,aux):
    if n==1:
        print(f"Move disk 1: {src} → {dst}")
        return
    hanoi(n-1,src,aux,dst)
    print(f"Move disk {n}: {src} → {dst}")
    hanoi(n-1,aux,dst,src)
hanoi(3,"A","C","B")

memo={}
def fib(n):
    if n in memo: return memo[n]
    if n<=1: return n
    memo[n]=fib(n-1)+fib(n-2)
    return memo[n]
print([fib(i) for i in range(11)])

def profile(**kwargs):
    print("Student Profile:")
    for k,v in kwargs.items():
        print(f"  {k.capitalize():12}: {v}")
profile(name="Alice",age=16,grade="A",city="Durgapur")

def fib_gen(n):
    a,b=0,1
    for _ in range(n):
        yield a
        a,b=b,a+b
print(list(fib_gen(10)))

def apply_n(fn,n,x):
    for _ in range(n): x=fn(x)
    return x
double=lambda x:x*2
print(apply_n(double,5,1))  # 32

def safe_div(a,b):
    try:
        return a/b
    except ZeroDivisionError:
        return "Cannot divide by zero"
    except TypeError:
        return "Invalid types"
print(safe_div(10,2))
print(safe_div(10,0))

lst=[10,20,30]
try:
    i=int(input("Index: "))
    print(lst[i])
except ValueError:
    print("Enter a valid integer")
except IndexError:
    print(f"Index out of range (0-{len(lst)-1})")

class InvalidAgeError(Exception):
    def __init__(self,age):
        super().__init__(f"Age {age} is invalid (must be 0-120)")
        self.age=age
def set_age(a):
    if not 0<=a<=120: raise InvalidAgeError(a)
    return a
try:
    print(set_age(int(input("Age: "))))
except InvalidAgeError as e:
    print(e)

def read_number():
    try:
        n=int(input("Enter number: "))
    except ValueError:
        print("Not a number!")
    else:
        print(f"Square: {n**2}")
    finally:
        print("Attempt complete.")
read_number()

filename=input("Filename: ")
try:
    with open(filename) as f:
        print(f.read())
except FileNotFoundError:
    print(f"File '{filename}' not found")
except PermissionError:
    print("Permission denied")

def load_data(filename):
    try:
        with open(filename) as f: return f.read()
    except FileNotFoundError as e:
        raise RuntimeError(f"Could not load {filename}") from e
try:
    load_data("missing.txt")
except RuntimeError as e:
    print(e)
    print("Caused by:", e.__cause__)

for attempt in range(3):
    try:
        n=int(input(f"Attempt {attempt+1}: Enter number: "))
        print(f"You entered: {n}")
        break
    except ValueError:
        print("Invalid! Try again.")
else:
    print("3 failed attempts. Giving up.")

data={"name":"Alice","age":16,"city":"Durgapur"}
for key in ["name","age","school","city"]:
    try:
        print(f"{key}: {data[key]}")
    except KeyError:
        print(f"{key}: NOT FOUND")

exceptions=[ZeroDivisionError,ValueError,TypeError,IndexError,KeyError]
print("Exception hierarchy:")
for exc in exceptions:
    chain=[]
    cls=exc
    while cls:
        chain.append(cls.__name__)
        cls=cls.__bases__[0] if cls.__bases__ else None
    print(" -> ".join(chain))

import io
log=io.StringIO()
operations=[(10,2),(5,0),(int,"abc"),(["a"],1)]
for op in operations:
    try:
        if len(op)==2 and isinstance(op[0],int):
            result=op[0]/op[1]
            print(f"{op[0]}/{op[1]}={result}")
    except Exception as e:
        msg=f"ERROR: {type(e).__name__}: {e}"
        log.write(msg+"\n")
        print(msg)
print("\nLog:",log.getvalue())

filename=input("Filename: ")
try:
    with open(filename) as f:
        content=f.read()
    lines=content.splitlines()
    words=content.split()
    print(f"Lines: {len(lines)}")
    print(f"Words: {len(words)}")
    print(f"Chars: {len(content)}")
except FileNotFoundError:
    print("File not found")

students=[("Alice",90),("Bob",75),("Carol",88)]
with open("students.txt","w") as f:
    for name,marks in students:
        f.write(f"{name},{marks}\n")
print("Records written. Reading back:")
with open("students.txt") as f:
    for line in f:
        name,marks=line.strip().split(",")
        print(f"{name}: {marks}")

with open("log.txt","a") as f:
    import datetime
    f.write(f"{datetime.datetime.now()}: Program started\n")
with open("log.txt") as f:
    print(f.read())

keyword=input("Search keyword: ")
try:
    with open("data.txt") as f:
        matches=[l for l in f if keyword.lower() in l.lower()]
    if matches:
        for i,l in enumerate(matches,1): print(f"{i}: {l.strip()}")
    else:
        print("Not found")
except FileNotFoundError:
    print("File not found")

src="source.txt"
dst="copy.txt"
with open(src,"w") as f: f.write("Hello\nWorld\nPython")
with open(src) as f, open(dst,"w") as g:
    content=f.read()
    g.write(content)
print("Source:",open(src).read())
print("Copy:",open(dst).read())

with open("essay.txt","w") as f:
    f.write("the cat sat on the mat the cat")
with open("essay.txt") as f:
    words=f.read().split()
freq={}
for w in words: freq[w]=freq.get(w,0)+1
for k,v in sorted(freq.items(),key=lambda x:-x[1]):
    print(f"{k:15}: {v}")

for name,content in [("a.txt","File A\n"),("b.txt","File B\n")]:
    with open(name,"w") as f: f.write(content)
with open("merged.txt","w") as out:
    for name in ["a.txt","b.txt"]:
        with open(name) as f:
            out.write(f.read())
print(open("merged.txt").read())

data=[("Name","Age","City"),("Alice",16,"Delhi"),("Bob",17,"Mumbai")]
with open("data.csv","w") as f:
    for row in data:
        f.write(",".join(str(x) for x in row)+"\n")
with open("data.csv") as f:
    for line in f:
        print(line.strip().split(","))

with open("sample.txt","w") as f:
    f.write("Hello\nThis is a longer line\nShort")
with open("sample.txt") as f:
    lines=f.readlines()
longest=max(lines,key=len)
print(f"Longest line ({len(longest.strip())} chars):",longest.strip())

import datetime
entry=input("Diary entry: ")
with open("diary.txt","a") as f:
    f.write(f"[{datetime.date.today()}] {entry}\n")
print("Saved. All entries:")
with open("diary.txt") as f:
    print(f.read())