CODEWITHSUNDEEP
formatpython
Lekensteyn
Lekensteyn

Reputation: 66515

What is the pythonic way to print values right aligned?

I've a list of strings which I want to group by their suffix and then print the values right-aligned, padding the left side with spaces.

What is the pythonic way to do that?

My current code is:

def find_pos(needle, haystack):
    for i, v in enumerate(haystack):
        if str(needle).endswith(v):
            return i
    return -1

# Show only Error and Warning things
search_terms = "Error", "Warning"
errors_list = filter(lambda item: str(item).endswith(search_terms), dir(__builtins__))

# alphabetical sort
errors_list.sort()
# Sort the list so Errors come before Warnings
errors_list.sort(lambda x, y: find_pos(x, search_terms) - find_pos(y, search_terms))

# Format for right-aligning the string
size = str(len(max(errors_list, key=len)))
fmt = "{:>" + size + "s}"
for item in errors_list:
    print fmt.format(item)

An alternative I had in mind was:

size = len(max(errors_list, key=len))
for item in errors_list:
    print str.rjust(item, size)

I'm still learning Python, so other suggestions about improving the code is welcome too.

Upvotes: 2

Views: 1279

Answers (3)

Ignacio Vazquez-Abrams
Ignacio Vazquez-Abrams

Reputation: 799470

Very close.

fmt = "{:>{size}s}"
for item in errors_list:
    print fmt.format(item, size=size)

Upvotes: 8

Sven Marnach
Sven Marnach

Reputation: 602685

  1. The two sorting steps can be combined into one:

    errors_list.sort(key=lambda x: (x, find_pos(x, search_terms)))

    Generally, using the key parameter is preferred over using cmp. Documentation on sorting

  2. If you are interested in the length anyway, using the key parameter to max() is a bit pointless. I'd go for

    width = max(map(len, errors_list))

  3. Since the length does not change inside the loop, I'd prepare the format string only once:

    right_align = ">{}".format(width)

  4. Inside the loop, you can now do with the free format() function (i.e. not the str method, but the built-in function):

    for item in errors_list:
    print format(item, right_align)

  5. str.rjust(item, size) is usually and preferrably written as item.rjust(size).

Upvotes: 7

samb8s
samb8s

Reputation: 437

You might want to look here, which describes how to right-justify using str.rjust and using print formatting.

Upvotes: 1

Related Questions