In Python f-strings, placeholders are enclosed in curly braces {} and can contain various format specifiers and expressions to format values. Here are some common placeholders and format specifiers you can use within f-strings:

1. Basic Value Insertion:

   • {variable}: Insert the value of the variable.
   • {expression}: Insert the result of the expression.

2. String Formatting:

   • {variable:s}: Insert the value of the variable as a string.
   • {variable:<width}: Left-align the string within a field of the specified width.
   • {variable:^width}: Center-align the string within a field of the specified width.
   • {variable:>width}: Right-align the string within a field of the specified width.
   • {variable:.precisionf}: Format a floating-point number with the specified precision.
   • {variable:.precisions}: Format a string with the specified length (right-padded with spaces if needed).

3. Integer Formatting:

   • {variable:d}: Insert the value of the variable as an integer.
   • {variable:widthd}: Format an integer with a minimum field width.
   • {variable:0widthd}: Format an integer with leading zeros.

4. Floating-Point Formatting:

   • {variable:f}: Insert the value of the variable as a floating-point number.
   • {variable:.precisionf}: Format a floating-point number with the specified precision.
   • {variable:e}: Format a floating-point number in scientific notation.
   • {variable:.precisione}: Format a floating-point number in scientific notation with the specified precision.

5. Hexadecimal and Binary Formatting:

   • {variable:x}: Format an integer as a hexadecimal string (lowercase).
   • {variable:X}: Format an integer as a hexadecimal string (uppercase).
   • {variable:b}: Format an integer as a binary string.

6. Date and Time Formatting:

   • {variable:%format}: Format a datetime object using Python's strftime format.

For example, here's how you can use some of these placeholders and format specifiers in f-strings:

name = "Alice"
age = 30
pi = 3.14159

print(f"Hello, {name}! You are {age} years old.")
print(f"Value of pi: {pi:.2f}")
print(f"Binary representation of 10: {10:b}")