DICTIONARY OPERATIONS AND MET……
Operations and Methods
Dictionary operations என்பது dictionary-ல் data-ஐ: create access add update delete search iterate copy combine செய்ய பயன்படுத்தப்படும் basic actions. Dictionary methods என்பது dictionary object-க்கு Python already provide செய்திருக்கும் bu…
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Definition
Dictionary operations என்பது dictionary-ல் data-ஐ: create access add update delete search iterate cop……
Explanation
Example
student = { "name": "Arun", "age": 20, "mark": 85 } M……
Simple Explanation
Dictionary: student = { "name": "Arun", "age": 20, "mark": 85 } இதைக் ஒரு student record என்று நினைத்துக்கொள்……
Explanation
Basic dictionary
student = { "name": "Ravi", "age": 21, "mark": 90 } Structu……
Explanation
Operation 1 create dictionary
Dictionary create செய்ய: stud……
Program
or
Explanation
Operation 2 access value
Value access செய்ய key பயன்படுத்த வேண்டும……
Here: student → dictionary "n……
Explanation
Access using get
Another method: print(student……
Difference மிகவும் important. Using: stu……
Explanation
Get with default
student = { "name": "Arun" } ……
Definition
Meaning
age key exists → actual value……
Explanation
Operation 3 add item
New key-value pair add செய்ய: studen……
Explanation
How add works
student["age"] = 20 Python check……
Explanation
Operation 4 update value
Existing key-ன் value மாற்ற: student = { ……
Program
Old
Program
New
Comparison
Add vs update
Same syntax: dictionary[key] =……
Explanation
Example
student["city"] = "Madurai" If city இல்லைய……
Explanation
Operation 5 delete using del
student = { "name": "Arun", "age"……
del removes specified key-val……
Explanation
Delete entire dictionary
del student இதனால் entire var……
Common Mistake
Error
NameError…
Explanation
Operation 6 membership
Dictionary-ல் key இருக்கிறதா என்று check செ……
Program
Example
Explanation
Not in
print("city" not in student) ……
Important
Important in operator
Dictionary-ல்: "name" in stud……
Program
Example
Because "Arun" is a value. To……
Explanation
Operation 7 length
student = { "name": "Arun", "……
Explanation
Operation 8 iteration
Dictionary-ஐ for loop மூலம் iterate செய்யலாம். st……
Important
By default dictionary iterati……
Explanation
Loop keys
for key in student.keys(): pr……
Explanation
Loop values
for value in student.values()……
Explanation
Loop items
for key, value in student.ite……
This is very important.…
Explanation
How items works
student.items() produces pairs like: ("name", "Arun") ("age", 20) ("mark", 90) Then: for key, value……
Explanation
Dictionary methods
Main dictionary methods: get() keys() values() items() update() po……
Program
Example
No error.…
Comparison
Get vs square bracket
Using: student["mark"] Missing key: KeyError Using:……
Explanation
Method 2 keys
Returns all keys. student = { "name……
Explanation
Keys loop
for key in student.keys(): pr……
Explanation
Method 3 values
Returns all values. print(stu……
Explanation
Values loop
for value in student.values()……
Explanation
Method 4 items
Returns key-value pairs. prin……
Each pair is represented like……
Important
Most important items use
for key, value in student.ite……
Remember
keys() → Key only values() → ……
Explanation
Method 5 update
update() adds or modifies mul……
Program
Example
Explanation
student.update({ "age": 20, "……
Explanation
Update existing
student = { "name": "Arun", "mark……
Existing key update ஆகிறது.…
Explanation
Update multiple items
student.update({ "age": 20, "city": "Chenn……
Explanation
Method 6 pop
pop() removes specified key and returns its value. student ……
Flow
Pop flow
student.pop("mark") does two ……
Flow
1. Finds "mark" 2. Removes it……
Output
Result
Explanation
Pop missing key
student.pop("city") If city key absent: Key……
Explanation
Method 7 popitem
popitem() removes the last inserted key-value pair. studen……
Important
popitem() returns: (key, valu……
Comparison
Pop vs popitem
Explanation
Example
student.pop("age") removes age.……
Explanation
Method 8 clear
Removes all items. student = { "na……
Dictionary variable still exi……
Comparison
Clear vs del
student.clear()…
Output
Result
Variable exists. But: del stu……
Explanation
Method 9 copy
Creates a shallow copy. student = { "name":……
Comparison
Assignment vs copy
This is important. a = { "mark": 80 } b = a……
Why? a ──┐ ├── Same object b ……
Explanation
Syntax
dictionary.setdefault(key, default_value) If key ex……
Program
Example
Explanation
Setdefault existing key
student = { "name": "Arun", "age……
Why? age already exists. It d……
Comparison
Setdefault vs update
Output
Result
But: student.setdefault("age"……
Output
Result
Because setdefault() keeps ex……
Explanation
Method 11 fromkeys
Creates a new dictionary using a sequence ……
All keys receive same value.…
Explanation
Fromkeys without value
keys = ["a", "b", "c"] data =……
Default value is: None…
Explanation
Operation 9 merging dictionaries
Modern Python supports dictionary mergi……
Explanation
Merging with duplicate key
a = { "x": 10 } b = { "x": 50……
Right-side dictionary value w……
Explanation
Update merge
We can also merge using: a.up……
Program
Example
Explanation
a.update(b)…
Comparison
Difference
Comparison
Operation 10 comparison
Dictionaries can be compared using ==. ……
Dictionary equality mainly checks same key-va……
Explanation
Dictionary comprehension
Dictionary can be created using comprehe……
Dry Run
Dry run comprehension
Explanation
Nested dictionary operation
students = { "s1": { "name": "Arun", "mark": 90 }……
Explanation
Update nested value
students["s1"]["mark"] = 95 N……
Explanation
For loop nested dictionary
for sid, data in students.items(): pr……
Output
Possible output
Table
Dictionary method summary
Table
Operations summary
Important
Important difference 1
d["key"] versus: d.get("key") M……
Important
Important difference 2
d.pop("key") versus: d.popitem() pop(key……
Important
Important difference 3
d.clear() versus: del d clear() → items……
Important
Important difference 4
b = a versus: b = a.copy() b = a → sa……
Important
Important difference 5
keys() returns: keys values() r……
Common Mistake
Common error 1
d = { "name": "Arun" } print(……
Common Mistake
Error
KeyError Better: print(d.get(……
Common Mistake
Common error 2
d = { "a": 1, "b": 2 } for x in d: print(x) Some stude……
Common Mistake
Common error 3
d = {"a": 1} d.remove("a") Wrong. Dictionary ……
Common Mistake
Common error 4
d = {"a": 1} d.append({"b": 2}) Wrong. Dict……
Common Mistake
Common error 5
Trying positional access: d = { "name": "Arun"……
Important
Remember dictionary method categories. Reading Methods get() keys() values() items(……
Memory Trick
Remember this sequence: G K V I G → get() K → keys() V → values() I → ite……
TRB Point
Trb point 1
What is output? d = { "a": 10……
TRB Point
Trb point 2
d = { "a": 10, "b": 20 } prin……
TRB Point
Trb point 3
d = { "a": 10, "b": 20 } prin……
TRB Point
Trb point 4
d = { "a": 10, "b": 20 } print(d.items(……
TRB Point
Trb point 5
d = { "a": 10 } x = d.pop("a"……
TRB Point
Trb point 6
d = { "a": 1, "b": 2 } x = d.……
in modern Python insertion-or……
TRB Point
Trb point 7
What is returned by: d.clear()…
Important
clear() modifies the dictiona……
Program
Example
TRB Point
Trb point 8
What does this do? d.setdefault("x", 10) If "x"……
Interview Point
Interview point 1
Difference between get() and setdefault()? get(): d.get("age", 20) Missing key-க்கு 20 retu……
Program
Example
No insertion. But:…
Insertion happens.…
Interview Point
Interview point 3
Do keys(), values(), and items() return lists? No. They retur……
Program
Example
MCQ
Which method gets a value wit……
MCQ
Which returns all keys?…
MCQ
Which returns all values?…
MCQ
Which method returns key-valu……
MCQ
Which method removes a specif……
MCQ
Which method removes the last……
MCQ
Which method removes all dict……
MCQ
What does copy() create?…
MCQ
What is output? d = {"a": 10}…
MCQ
What happens? d = {"a": 10}…
MCQ
What is output? d = {}…
Mcq 12
What does this return? dict.fromkeys(["a", "b"]) ……
Practice
Practice 1
Predict output: d = { "name": "R……
Practice
Practice 2
d = { "a": 1 } d["b"] = 2 pri……
Practice
Practice 3
d = { "a": 10, "b": 20 } d["a……
Practice
Practice 4
d = { "a": 1, "b": 2 } for ke……
Practice
Practice 5
d = { "a": 1, "b": 2 } x = d.……
Summary
Dictionary operations mainly include: Create Access Add Update Delete Search Loop Merge Compare Core syntax: ……
Explanation
Short description
Dictionary Operations and Methods = Dictionary data-ஐ access, mod……
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