In Python, you can adjust the case of strings using the upper() and lower() methods.

The upper() method converts all characters in a string to uppercase:

text = "hello, world!"
uppercase_text = text.upper()
print(uppercase_text)  # Output: "HELLO, WORLD!"

The lower() method converts all characters in a string to lowercase:

text = "HELLO, WORLD!"
lowercase_text = text.lower()
print(lowercase_text)  # Output: "hello, world!"

You can also adjust the case of specific characters in a string using slicing and concatenation. For example, to capitalize the first letter of a string, you can use:

text = "hello, world!"
capitalized_text = text[0].upper() + text[1:]
print(capitalized_text)  # Output: "Hello, world!"

Here, we slice the first character of the string (text[0]) and capitalize it using the upper() method. We then concatenate this capitalized character with the rest of the string (text[1:]), which we leave unchanged.

Similarly, you can lowercase the first letter of a string using:

text = "Hello, world!"
lowercase_text = text[0].lower() + text[1:]
print(lowercase_text)  # Output: "hello, world!"

Here, we lowercase the first character of the string (text[0]) using the lower() method and concatenate it with the rest of the string (text[1:]), which we leave unchanged.