Mastering Python : Day 5
Strings in Python
In Python, a string is a sequence of characters enclosed in quotes (single, double, or triple quotes). Strings are immutable, meaning they cannot be changed after creation.
String Methods in Python
Python provides a wide range of methods for manipulating and working with strings. Here are some of the most commonly used string methods:
1. len()
Returns the length of the string.
code1 my_string = "Hello, World!"
print(len(my_string)) # Output: 13
2. upper() and lower()
Converts the string to uppercase or lowercase.
code1my_string = "Hello, World!"
2print(my_string.upper()) # Output: "HELLO, WORLD!"
3print(my_string.lower()) # Output: "hello, world!"
3. strip()
Removes leading and trailing whitespace from the string.
code1my_string = " Hello, World! "
2print(my_string.strip()) # Output: "Hello, World!"
4. split()
Splits the string into a list of substrings based on a specified separator.
code1my_string = "apple,banana,cherry"
2print(my_string.split(",")) # Output: ["apple", "banana", "cherry"]
5. join()
Joins a list of strings into a single string.
code1my_list = ["apple", "banana", "cherry"]
2print(",".join(my_list)) # Output: "apple,banana,cherry"
6. find() and index()
Returns the index of the first occurrence of a specified substring.
code1my_string = "Hello, World!"
2print(my_string.find("World")) # Output: 7
3print(my_string.index("World")) # Output: 7
7. replace()
Replaces occurrences of a specified substring with another substring.
code1my_string = "Hello, World!"
2print(my_string.replace("World", "Universe")) # Output: "Hello, Universe!"
Practice Questions on Strings in Python
Here are some practice questions to help you reinforce your understanding of strings in Python:
1. String Concatenation
Write a Python program to concatenate two strings "Hello, " and "World!" using the + operator.
code1# Your code here
2. String Repetition
Write a Python program to repeat the string "Hello, World!" three times using the * operator.
pythonVerifyOpen In EditorEditCopy code1# Your code here
3. String Indexing
Write a Python program to extract the first character of the string "Hello, World!" using indexing.
code1# Your code here
4. String Slicing
Write a Python program to extract the substring "World" from the string "Hello, World!" using slicing.
code1# Your code here
5. String Formatting
Write a Python program to format the string "My name is {} and I am {} years old." with the values "John" and 30 using the format() method.
code1# Your code here
6. String Splitting
Write a Python program to split the string "apple,banana,cherry" into a list of substrings using the comma as a separator.
code1# Your code here
7. String Joining
Write a Python program to join the list of strings ["apple", "banana", "cherry"] into a single string using the comma as a separator.
code1# Your code here
8. String Searching
Write a Python program to find the index of the first occurrence of the substring "World" in the string "Hello, World!".
code1# Your code here
9. String Replacing
Write a Python program to replace all occurrences of the substring "World" with "Universe" in the string "Hello, World!".
code1# Your code here
10. String Validation
Write a Python program to check if the string "Hello, World!" contains only alphanumeric characters.
code1# Your code here
| String Methods: |
| Method | Description |
| capitalize() | Converts the first character to upper case |
| casefold() | Converts string into lower case |
| center() | Returns a centered string |
| count() | Returns the number of times a specified value occurs in a string |
| encode() | Returns an encoded version of the string |
| endswith() | Returns true if the string ends with the specified value |
| expandtabs() | Sets the tab size of the string |
| find() | Searches the string for a specified value and returns the position of where it was found |
| format() | Formats specified values in a string |
| format_map() | Formats specified values in a string |
| index() | Searches the string for a specified value and returns the position of where it was found |
| isalnum() | Returns True if all characters in the string are alphanumeric |
| isalpha() | Returns True if all characters in the string are in the alphabet |
| isascii() | Returns True if all characters in the string are ascii characters |
| isdecimal() | Returns True if all characters in the string are decimals |
| isdigit() | Returns True if all characters in the string are digits |
| isidentifier() | Returns True if the string is an identifier |
| islower() | Returns True if all characters in the string are lower case |
| isnumeric() | Returns True if all characters in the string are numeric |
| isprintable() | Returns True if all characters in the string are printable |
| isspace() | Returns True if all characters in the string are whitespaces |
| istitle() | Returns True if the string follows the rules of a title |
| isupper() | Returns True if all characters in the string are upper case |
| join() | Joins the elements of an iterable to the end of the string |
| ljust() | Returns a left justified version of the string |
| lower() | Converts a string into lower case |
| lstrip() | Returns a left trim version of the string |
| maketrans() | Returns a translation table to be used in translations |
| partition() | Returns a tuple where the string is parted into three parts |
| replace() | Returns a string where a specified value is replaced with a specified value |
| rfind() | Searches the string for a specified value and returns the last position of where it was found |
| rindex() | Searches the string for a specified value and returns the last position of where it was found |
| rjust() | Returns a right justified version of the string |
| rpartition() | Returns a tuple where the string is parted into three parts |
| rsplit() | Splits the string at the specified separator, and returns a list |
| rstrip() | Returns a right trim version of the string |
| split() | Splits the string at the specified separator, and returns a list |
| splitlines() | Splits the string at line breaks and returns a list |
| startswith() | Returns true if the string starts with the specified value |
| strip() | Returns a trimmed version of the string |
| swapcase() | Swaps cases, lower case becomes upper case and vice versa |
| title() | Converts the first character of each word to upper case |
| translate() | Returns a translated string |
| upper() | Converts a string into upper case |
| zfill() | Fills the string with a specified number of 0 values at the beginning |