Python Basics 2

String Concatenation, Indexing, Slicing...

Index

1. String Concatenation

2. Indexing

3. Slicing

4. Advanced Slicing

5. String Functions

6. Conditional Statements

7. Indentation

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1. String Concatenation

Definition:
String concatenation in Python refers to the operation of joining two or more strings end-to-end to form a single string.

Syntax:

python

string1 + string2 + ... + stringN

Examples:

• Basic Example:

greeting = "Hello" + " " + "World" 

print(greeting)

Output:Hello World

• Advanced Example:

name = "Vishal" 

full_greeting = "Hello, " + name + "!" print(full_greeting)

Output:Hello, Vishal!

Rules:

• Only strings can be concatenated using the + operator. Attempting to concatenate other data types will raise a TypeError unless they are explicitly converted to strings.

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2. Indexing

Definition:
Indexing refers to accessing individual characters in a string using their position. Python uses zero-based indexing, where the first character has an index of 0.

Syntax:

string_variable[index]

Examples:

• Basic Example:

word = "Python" 

print(word[0])

Output:P

• Advanced Example:

word = "Python" 

print(word[-1])

Output:n

Rules:

• Positive indices count from the start, and negative indices count from the end of the string.

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3. Slicing

Definition:
Slicing allows you to access a substring by specifying a start and end index. The slice includes characters from the start index up to, but not including, the end index.

Syntax:

string_variable[start:end]

Examples:

• Basic Example:

word = "Python" 

print(word[1:4])

Output:yth

• Advanced Example:

word = "Python" 

print(word[:4])

Output:Pyth

Rules:

• Omitting the start index defaults to 0, and omitting the end index slices to the end of the string.

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4. Advanced Slicing

Definition:
Advanced slicing allows you to extract elements from a string using a step, which specifies how many characters to skip.

Syntax:

string_variable[start:end:step]

Examples:

• Basic Example:

word = "Python" 

print(word[::2])

Output:Pto

• Advanced Example:

word = "Python" 

print(word[::-1])

Output:nohtyP

Rules:

• A negative step value reverses the direction of the slicing.

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5. String Functions

Definition:
String functions are built-in methods in Python that allow various operations such as transforming, searching, and formatting strings.

Common String Functions:

• lower(): Converts all characters to lowercase.

• upper(): Converts all characters to uppercase.

• strip(): Removes leading and trailing whitespace.

• find(): Searches for a substring and returns its first occurrence index.

• replace(): Replaces occurrences of a substring with another substring.

Syntax:

string_variable.method(arguments)

Examples:

• Basic Example:

text = "Hello World" 

print(text.lower())

Output:hello world

• Advanced Example:

text = "Hello World" 

new_text = text.replace("World", "Python") 

print(new_text)

Output:Hello Python

Rules:

• String methods do not modify the original string; they return a new string.

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6. Conditional Statements

Definition:
Conditional statements allow decision-making in Python by executing code blocks based on whether a condition is true or false.

Syntax:

if condition: # code block 

elif another_condition: # another code block 

else: # final code block

Examples:

• Basic Example:

x = 10 if x > 5: 

print("x is greater than 5")

Output:x is greater than 5

Advanced Example:

x = 10 if x > 15: 

print("x is greater than 15") 

elif x > 5: 

print("x is greater than 5 but less than or equal to 15") 

else: print("x is 5 or less")

Output:x is greater than 5 but less than or equal to 15

Rules:

• Conditional statements require proper indentation to define code blocks.

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7. Indentation

Definition:
Indentation in Python is crucial as it defines the structure and hierarchy of the code. Unlike other programming languages that use braces or keywords, Python uses indentation to group statements.

Syntax:

if condition: # indented code block statement

Examples:

• Basic Example:

x = 5 

if x > 0: 

print("x is positive")

Output:x is positive

• Advanced Example:

x = 5 if x > 0: 

print("x is positive") 

if x > 3: 

print("x is greater than 3")

Output:x is positivex is greater than 3

Rules:

• Consistent use of spaces or tabs is essential. Mixing them can lead to errors.

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This issue of FM University introduces essential Python string operations and flow control mechanisms, providing a solid foundation for your coding journey. Continue exploring these concepts to enhance your Python skills!

- Vishal Rajput