I have few ruby strings, which I want to align left and right appropriately.
I'm now using "Name".center(20, " ") to get "(7 spaces)Name(8 spaces)"
How can I achieve "Name(15 spaces)" or "(15 spaces)Name"
Thanks.
"Name".ljust(19)
"Name".rjust(19)
Ruby has a printf method defined in Kernel, try using that.
It supports many common "f" ("format", like in scanf, printf, ...) options (see e.g. man 3 printf).
Left and right justification can be done like this (extracted from comment):
printf("%10s", "right")
printf("%-10s","left")
Insert n Copies of a Character
There are certainly other ways to do this, but one of them is to use the splat operator to copy a character (e.g. the space character) a certain number of times. For example:
puts (' ' * 15) + 'Name'
puts 'Name' + (' ' * 15)
Related
What's the best way to truncate a string to the first n words?
n = 3
str = "your long long input string or whatever"
str.split[0...n].join(' ')
=> "your long long"
str.split[0...n] # note that there are three dots, which excludes n
=> ["your", "long", "long"]
You could do it like this:
s = "what's the best way to truncate a ruby string to the first n words?"
n = 6
trunc = s[/(\S+\s+){#{n}}/].strip
if you don't mind making a copy.
You could also apply Sawa's Improvement (wish I was still a mathematician, that would be a great name for a theorem) by adjusting the whitespace detection:
trunc = s[/(\s*\S+){#{n}}/]
If you have to deal with an n that is greater than the number of words in s then you could use this variant:
s[/(\S+(\s+)?){,#{n}}/].strip
You can use str.split.first(n).join(' ')
with n being any number.
Contiguous white spaces in the original string are replaced with a single white space in the returned string.
For example, try this in irb:
>> a='apple orange pear banana pineaple grapes'
=> "apple orange pear banana pineaple grapes"
>> b=a.split.first(2).join(' ')
=> "apple orange"
This syntax is very clear (as it doesn't use regular expression, array slice by index). If you program in Ruby, you know that clarity is an important stylistic choice.
A shorthand for join is *
So this syntax str.split.first(n) * ' ' is equivalent and shorter (more idiomatic, less clear for the uninitiated).
You can also use take instead of first
so the following would do the same thing
a.split.take(2) * ' '
This could be following if it's from rails 4.2 (which has truncate_words)
string_given.squish.truncate_words(number_given, omission: "")
I am currently doing a bunch of processing on a string using regular expressions with gsub() but I'm chaining them quite heavily which is starting to get messy. Can you help me construct a single regex for the following:
string.gsub(/\.com/,'').gsub(/\./,'').gsub(/&/,'and').gsub(' ','-').gsub("'",'').gsub(",",'').gsub(":",'').gsub("#39;",'').gsub("*",'').gsub("amp;",'')
Basically the above removes the following:
.com
.
,
:
*
switches '&' for 'and'
switches ' ' for '-'
switches ' for ''
Is there an easier way to do this?
You can combine the ones that remove characters:
string.gsub(/\.com|[.,:*]/,'')
The pipe | means "or". The right side of the or is a character class; it means "one of these characters".
A translation table is more scalable as you add more options:
translations = Hash.new
translations['.com'] = ''
translations['&'] = 'and'
...
translations.each{ |from, to| string.gsub from, to }
Building on Tim's answer:
You can pass a block to String.gsub, so you could combine them all, if you wanted:
string.gsub(/\.com|[.,:*& ']/) do |sub|
case(sub)
when '&'
'and'
when ' '
'-'
else
''
end
end
Or, building off echoback's answer, you could use a translation hash in the block (you may need to call translations.default = '' to get this working):
string.gsub(/\.com|[.,:*& ']/) {|sub| translations[sub]}
The biggest perk of using a block is only having one call to gsub (not the fastest function ever).
Hope this helps!
I can't iterate over the entire range of unicode characters.
I searched everywhere...
I am building a fuzzer and want to embed into a url, all unicode characters (one at a time).
For example:
http://www.example.com?a=\uff1c
I know that there are some built tools but I need more flexibility.
If i could do someting like the following: "\u" + "ff1c" it would be great.
This is the closest I got:
char = "\u0000"
...
#within iteration
char.succ!
...
but after the character "\u0039", which is the number 9, I will get "10" instead of ":"
You could use pack to convert numbers to UTF8 characters but I'm not sure if this solves your problem.
You can either create an array with numeric values of all the characters and use pack to get an UTF8 string or you can just loop from 0 to whatever you need and use pack within the loop.
I've written a small example to explain myself. The code below prints out the hex value of each character followed by the character itself.
0.upto(100) do |i|
puts "%04x" % i + ": " + [i].pack("U*")
end
Here's some simpler code, albeit slightly obfuscated, that takes advantage of the fact that Ruby will convert an integer on the right hand side of the << operator to a codepoint. This only works with Ruby 1.8 up for integer values <= 255. It will work for values greater than 255 in 1.9.
0.upto(100) do |i|
puts "" << i
end
I want to extract the quoted substrings from inside a string. This is an example:
string = 'aaaa' + string_var_x + 'bbbb' + string_var_y
The output after parsing should be:
["'aaaa'", "'bbbb'"]
The initial solution was to string.scan /'\w'/ which is almost ok.
Still I can't get it working on more complex string, as it's implied that inside '...' there can be any kind of characters (including numbers, and !##$%^&*() whatever).
Any ideas?
I wonder if there's some way to make /'.*'/ working, but make it less greedy?
Lazy should fix this:
/'.*?'/
Another possibility is to use this:
/'[^']*'/
An alternate way to do it is:
>> %{string = 'aaaa' + string_var_x + 'bbbb' + string_var_y}.scan(/'[^'].+?'/)
#=> ["'aaaa'", "'bbbb'"]
String.scan gets overlooked a lot.
I'm outputting a set of numbered files from a Ruby script. The numbers come from incrementing a counter, but to make them sort nicely in the directory, I'd like to use leading zeros in the filenames. In other words
file_001...
instead of
file_1
Is there a simple way to add leading zeros when converting a number to a string? (I know I can do "if less than 10.... if less than 100").
Use the % operator with a string:
irb(main):001:0> "%03d" % 5
=> "005"
The left-hand-side is a printf format string, and the right-hand side can be a list of values, so you could do something like:
irb(main):002:0> filename = "%s/%s.%04d.txt" % ["dirname", "filename", 23]
=> "dirname/filename.0023.txt"
Here's a printf format cheat sheet you might find useful in forming your format string. The printf format is originally from the C function printf, but similar formating functions are available in perl, ruby, python, java, php, etc.
If the maximum number of digits in the counter is known (e.g., n = 3 for counters 1..876), you can do
str = "file_" + i.to_s.rjust(n, "0")
Can't you just use string formatting of the value before you concat the filename?
"%03d" % number
Use String#next as the counter.
>> n = "000"
>> 3.times { puts "file_#{n.next!}" }
file_001
file_002
file_003
next is relatively 'clever', meaning you can even go for
>> n = "file_000"
>> 3.times { puts n.next! }
file_001
file_002
file_003
As stated by the other answers, "%03d" % number works pretty well, but it goes against the rubocop ruby style guide:
Favor the use of sprintf and its alias format over the fairly
cryptic String#% method
We can obtain the same result in a more readable way using the following:
format('%03d', number)
filenames = '000'.upto('100').map { |index| "file_#{index}" }
Outputs
[file_000, file_001, file_002, file_003, ..., file_098, file_099, file_100]