question related to formatting . Usage of format() in python

The format() method formats the specified value(s) and insert them inside the string's placeholder.

txt1 = "My name is {fname}, I'm {age}".format(fname = "John", age = 36)

Here fname will be replaced by John and age will be replaced by 36, if you print txt1.

Alternatively you can use f strings . eg:

fname= "John"
age= 36
print(f"My name is {fname}, I'm {age}")

Even it will print the same output.

You can regarding it as a kind of string replacement.

{} part in the string -> string.format() content

Definition: https://www.w3schools.com/python/ref_string_format.asp

A pratical example can be like this:

base_url = 'www.xxxx.com/test?page={}'
for i in range(10):
    url = base_url.format(i)
    do sth

Format is often applied as a str-type method: txt.format(...), where type(txt)='str'.

This function is used to insert values inside string's placeholders. Placeholders are curly brackets {} placed inside a string and the format() method returns a formatted string with the values plugged into the string.

This function also enables formatting different type of variables in different ways. E.g. float with value 0.0001 can be represented in floating point representation: 0.0001 or scientific representation 1e-4 using different specifires.

Usage:

txt = "My name is {name}. I'm {age} years old."
print(txt.format(name="Dan", age=32))

Will output: 'My name is Dan. I'm 32 years old.'

You can use positional arguments as well:

txt = "My name is {}. I'm {} years old."
print(txt.format("Dan", 32))

Where the values are taken by their order. This will output the same result.

To format with different formatting you can use specifiers:

txt = "Decimal numbers: {number:d}"
print(txt.format(number=8340))

txt = "Fix point numbers: {number:.2f}"
print(txt.format(number=3.1415))

There are other specifiers that have other formatting behavior like centering some value to match some desired width:

txt = "{center:^20}"
print(txt.format(center='center'))

This will output ' center ' which contains exactly 20 characters.

There are many more formatting options that you can browse here or in many other rescorces.