How python interprets fstring width & zero padding?

Question

I'm a newbie in python.

I am stuck at figuring out fstring workings

Example 1

for n in range(1,11):
    sentence = f"The value is {n:{n:1}}"
    print(sentence)

Output:

The value is 1
The value is  2
The value is   3
The value is    4
The value is     5
The value is      6
The value is       7
The value is        8
The value is         9
The value is         10

Example 2

for n in range(1,11):
    sentence = f"The value is {n:{n:02}}"
    print(sentence)

Output:

The value is 1
The value is 02
The value is 003
The value is 0004
The value is 00005
The value is 000006
The value is 0000007
The value is 00000008
The value is 000000009
The value is         10

Example 3

for n in range(1,11):
    sentence = f"The value is {n:{n:03}}"
    print(sentence)

Output:

The value is 1
The value is 02
The value is 003
The value is 0004
The value is 00005
The value is 000006
The value is 0000007
The value is 00000008
The value is 000000009
The value is 0000000010

What I really want to know is How fstring interprets width & precision? Why example 2 last loop hasn't been calculated with zero paddings?

If I am not wrong, Example 1 output is interpreted as width. Example 2 & Example 3 is padding zero.

Also, How I can code to get the width with zero paddings like this? Require Output:

The value is   01
The value is   02
The value is   03
The value is   04
The value is   05
The value is   06
The value is   07
The value is   08
The value is   09
The value is   10

Prayson W. Daniel · Accepted Answer · 2020-12-23 07:12:09Z

1

You could do:

for n in range(1,11):
    n = f'{n:0>2}'
    sentence = f"The value is {n:>5}"
    print(sentence)

{n:0>2} means pad with zero in front if n has digital less than two, while {n:>5} mean pad with 5 spaces in front of n. See Python f-string Documentation

edited Dec 23, 2020 at 7:12

answered Dec 23, 2020 at 6:57

Prayson W. Daniel

15.8k6 gold badges57 silver badges62 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Jacky · Accepted Answer · 2020-12-23 07:28:41Z

0

for n in range(1,11):
sentence = f"The value is {n:02}"
print(sentence)

You can change {n:02} to {n:03} or other to check the difference.

{n:0x} print a hex format.

answered Dec 23, 2020 at 7:28

Jacky

3363 silver badges11 bronze badges

Collectives™ on Stack Overflow

How python interprets fstring width & zero padding?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related