Python: Advanced String Functions Cheat Sheet with Examples

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Python: Advanced String Functions Cheat Sheet with Examples



1. startswith() Function

The startswith() function returns True if a string starts with the specified substring, else False.

Example 1:


text = "Python is fun"
print(text.startswith("Python"))

Output:


True

⚠️ Point to Remember:


text = "python is fun"
print(text.startswith("Python"))  # Case sensitive

Output:


False

2. endswith() Function

The endswith() function returns True if the string ends with the specified substring, else False.

Example 1:


text = "Learn Python"
print(text.endswith("Python"))

Output:


True

⚠️ Point to Remember:


text = "Learn Python Programming"
print(text.endswith("Python"))

Output:


False

3. split() Function

The split() function breaks a string into a list using a separator (default is space).

Example 1:


text = "apple banana mango"
print(text.split())

Output:


['apple', 'banana', 'mango']

Example 2 (Custom Separator):


data = "12,34,56"
print(data.split(","))

Output:


['12', '34', '56']

4. join() Function

The join() function joins the elements of a list into a single string with a specified separator.

Example 1:


words = ['apple', 'banana', 'cherry']
print("-".join(words))

Output:


apple-banana-cherry

✅ Special Use Case:

Joining characters in a string:


text = "abc"
print(",".join(text))

Output:


a,b,c

5. isalnum() Function

The isalnum() function returns True if all characters in a string are alphanumeric (A-Z, a-z, 0-9), with no spaces or symbols.

Example 1:


print("abc123".isalnum())

Output:


True

Example 2 (With Symbol):


print("abc@123".isalnum())

Output:


False

⚠️ Point to Remember:

Spaces are not alphanumeric:


print("abc 123".isalnum())

Output:


False

6. isalpha() Function

The isalpha() function returns True if all characters in a string are alphabets (A–Z or a–z) and there are no digits, spaces, or special characters.

Example 1:


text = "Python"
print(text.isalpha())

Output:


True

Example 2 (with space):


text = "Python Code"
print(text.isalpha())

Output:


False

⚠️ Point to Remember:

Even spaces and numbers will make it return False.

7. isdigit() Function

The isdigit() function returns True if all characters in a string are digits (0–9).

Example 1:


num = "123456"
print(num.isdigit())

Output:


True

Example 2 (with space):


num = "123 456"
print(num.isdigit())

Output:


False

8. removeprefix() Function

The removeprefix() function removes the specified prefix from the beginning of the string, if it exists. This method was introduced in Python 3.9.

Example 1:


text = "unwantedText"
print(text.removeprefix("un"))

Output:


wantedText

Example 2 (prefix not present):


text = "hello"
print(text.removeprefix("un"))

Output:


hello

⚠️ Point to Remember:

This method does not affect the string if the prefix is not found.

9. center() Function

The center() function returns a new string of a specified width with the original string centered and padded with a fill character (default is space).

Example 1:


text = "Python"
print(text.center(20))

Output:


       Python

Example 2 (using * as fill character):


text = "Python"
print(text.center(20, "*"))

Output:


*******Python*******

⚠️ Point to Remember:

If the specified width is less than the string length, it returns the original string.

10. casefold() Function

The casefold() function is similar to lower() but is more aggressive. It is used for **case-insensitive comparisons**, especially in different languages.

Example 1:


text = "PYTHON"
print(text.casefold())

Output:


python

Example 2 (for comparison):


str1 = "Straße"
str2 = "STRASSE"
print(str1.casefold() == str2.casefold())

Output:


True

✅ Special Use Case:

casefold() is ideal for comparing strings in **Unicode**, like German "ß".

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    Stage 1: Python & Programming Fundamentals 
    
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1. Python & Programming Fundamentals
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1.1 Environment Setup
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    Stage 2: Mathematics for Machine Learning 
    
----------------------------------------
2. Mathematics for Machine Learning
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3. Data Handling & Preprocessing
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7. Natural Language Processing (NLP)
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8. Computer Vision (CV)
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----------------------------------------
9. Reinforcement Learning & Advanced Topics
----------------------------------------
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----------------------------------------
10. Deployment, Production & MLOps
----------------------------------------
10.1 Model Serving & APIs
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    Stage 11: Real-World Projects & Portfolio 
    
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11. Real-World Projects & Portfolio
----------------------------------------
11.1 Project Ideas by Domain
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    • Write blog posts/tutorials documenting your projects

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🛠 Tools: GitHub Pages, Streamlit, Heroku/Netlify, Docker
    Stage 12: Ethics, Explainability & Continuous Learning 
    
----------------------------------------
12. Ethics, Explainability & Continuous Learning
----------------------------------------
12.1 AI Ethics & Responsible AI
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12.2 Explainable AI (XAI)
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12.3 Continuous Learning & Staying Updated
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    • Reading codebases of popular libraries, exploring new architectures
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12.4 Advanced Research Topics (Optional/For Aspirants)
    • Research paper reading workflow
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    • Contributing to academic research or advanced industrial research

🛠 Tools: arXiv, Google Scholar alerts, RSS readers, community forums

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