Commonly Used String Methods in Python

Here is a list of string methods that are most commonly used while working with strings in Python. These methods help in formatting, cleaning, converting, searching, checking, and validating strings.

Common methods types:

  1. Case Formatting Methods
    • upper() Method
    • lower() Method
  2. Cleaning and Editing Methods
    • strip() Method
    • replace() Method
  3. Conversion Between String and List
    • split() Method
    • join() Method
  4. Searching Methods
    • find() Method
    • count() Method
  5. Check Methods
    • startswith() Method
    • endwith() Method
  6. Check Methods
    • isdigit() Method
    • isalpha() Method

1. upper() Method

The upper() method is used to convert all the characters in a string to uppercase. It returns a new string where all lowercase alphabets are changed to their uppercase form, while other characters (like numbers or symbols) remain unchanged.

Syntax:

string.upper()

Example:

text = "hello"
print(text.upper())
print(text)

Output:

HELLO

hello

Explanation:

  • The original string is "hello".
  • The upper() method converts all characters to uppercase: "HELLO".
  • These methods are non-destructive, meaning they do not change the original string. So, print(text) will still output "hello", not the uppercase version.

2. lower() Method

The lower() method is used to convert all the characters in a string to lowercase. It returns a new string in which all uppercase alphabets are converted to their lowercase form. Characters like numbers and special symbols remain unchanged.

Syntax:

string.lower()

Example:

text = "HELLO"
print(text.lower())

Output:

hello

Explanation:

  • The original string is "HELLO".
  • The lower() method converts it to all lowercase: "hello".

3. strip() Method

Removes spaces (or specified characters) from both ends of a string.

Syntax:

string.strip()

Note:
If no argument is given, it removes all spaces, tabs, and newline characters from both sides.

Example:

line = "  Shiksha Sanchar  "
cleaned = line.strip()
print(cleaned)

Output:

Shiksha Sanchar

Explanation:

  • There were extra spaces on both sides of the string.
  • strip() removed those spaces but not the ones between the words.

4. replace() Method

Replaces all matching parts (substring) with a new part.

Syntax:

string.replace(old, new)

Example:

text = "Python is easy. Python is powerful."
updated = text.replace("Python", "Java")
print(updated)

Output:

Java is easy. Java is powerful.

Explanation:

  • All "Python" words are replaced with "Java".
  • Original string stays the same. New string is stored in updated.

5. split() Method

Breaks the string into parts and gives a list.

Syntax:

string.split(separator)

Note:
If no separator is given, it uses space by default.

Example:

line = "Shiksha Sanchar is helpful"
words = line.split()
print(words)

Output:

['Shiksha', 'Sanchar', 'is', 'helpful']

Explanation:

  • The string is split wherever there is space.
  • Result is a list of words.

6. join() Method

Joins list items into one string using a separator.

Syntax:

separator.join(list)

Example:

words = ["Learn", "with", "ShikshaSanchar"]
sentence = " ".join(words)
print(sentence)

Output:

Learn with ShikshaSanchar

Explanation:

  • List elements are joined with space in between.
  • You can use any separator like "-", "+", etc.

7. find() Method

Searches the string for a specified value and returns the index of the first occurrence. Returns -1 if not found.

We can also specify the start and end positions to limit the search to a specific portion of the string.

Syntax:

string.find(substring, start, end)

Example:

text = "learning python is fun"
print(text.find("python"))
print(text.find("java"))

print(text.find("python", 0, 10))      # searches from index 0 to 9

Output:

9
-1
-1

Explanation:

  • "python" starts at index 9.
  • "java" is not found, so it returns -1.
  • Third time, it searches only from index 0 to 9, so "python" is not found → -1.

8. count() Method

Returns the number of times a specified value occurs in the string.

Syntax:

string.count(substring, start, end)

Example:

text = "banana"
print(text.count("a"))

Output:

3

Explanation:

  • The character 'a' appears 3 times in the word "banana".
  • count() helps in frequency analysis of substrings.

9. startswith() Method

The startswith() method checks whether a string starts with a specific prefix. It is case-sensitive means A and a are considered different. It returns True if the string starts with the given value; otherwise, it returns False.

Syntax:

string.startswith(prefix, start, end)

Parameters:

  • prefix – The string or tuple of strings to check at the start.
  • start (optional) – The position to start the search.
  • end (optional) – The position to end the search.

Example:

text = "python programming"
result1 = text.startswith("py")
result2 = text.startswith("gram", 7)
print(result1)
print(result2)

Output:

True
True

Explanation:

  • "python programming" starts with "py" → True
  • From index 7 onward, string is "gramming", which starts with "gram" → True

10. endswith() Method

The endswith() method checks whether a string ends with a specific suffix. It is case-sensitive means A and a are considered different. It returns True if the string ends with the given value; otherwise, it returns False.

Syntax:

string.endswith(suffix, start, end)

Parameters:

  • suffix – The string or tuple of strings to check at the end.
  • start (optional) – The position to start the search.
  • end (optional) – The position to end the search.

Example:

text = "python programming"
result1 = text.endswith("ing")
result2 = text.endswith("thon", 0, 6)
print(result1)
print(result2)

True
True

Explanation:

  • "python programming" ends with "ing" → True
  • text[0:6] is "python", which ends with "thon" → True

11. isalpha() Method

Returns True if all characters in the string are alphabetic (A-Z or a-z), otherwise False.

Syntax:

string.isalpha()

Example:

text1 = "Hello"
text2 = "Hello123"
print(text1.isalpha())
print(text2.isalpha())

Output:

True
False

Explanation:

  • text1 contains only letters, so it returns True.
  • text2 has numbers, so it returns False.

12. isdigit() Method

Returns True if all characters are digits (0–9), otherwise False.

Syntax:

string.isdigit()

Example:

text1 = "123"
text2 = "123abc"
print(text1.isdigit())
print(text2.isdigit())

Output:

True
False

Explanation:

  • text1 has only numbers, so it returns True.
  • text2 has letters, so it returns False.

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