1. List of Numbers to List of Strings
For example, we have this object:
In JavaScript, it's called Array
and in Python it's a List
.
And for some reason, we need to convert every member into String
. As you can see above, every member is a number (integer).
A. JavaScript
We can use the new method map()
to do that. Basic looping method using for
, while
, and do - while
can also do the task.
But of course, because map()
is designed to be sweeter than the basic methods, let's use it.
And BYAM!
Variable b
now consists of all members of variable a
, but each of them is now a string.
Use your browser console, and copy paste the code above. And then put console.log(b);
to see its content.
B. Python
In Python, when we design some structure which needs the conversion for some other process, we can use this shorthand:
As in:
That's it!
Well, not really.
You can use Python interpreter (command line) to print
the variable b
(the result).
It will have the same members as variable a
, but every (number) member is converted into a string.
To make it "safer", use this other shorthand to substitute the b
variable method:
- The
str()
is to convert anything to string. - The
v
is each member of variablea
. - The
a
is the input variable (list) we wanna convert. - And the square brackets,
[...]
, are to initiate alist
object.
2. The Other Way Round
A. JavaScript
For instance, we wanna extract the number only from an array which has that.
Let's use this object example:
It has string and number. Let's implement again the map()
method.
And variable b
now is the number part of every variable a
's member.
Wut?
- The
toString()
method is needed so when the method meets a non-string element, particularly thematch
method, it will have no problem for searching usingRegExp
. - The
match()
is theRegExp
searcher, with the\d+
pattern.
The\d
is the shorthand for digit (number). We can also use[0-9]
.
The plus sign+
is for pattern search for number that has 1 digit length or more.
Theg
flag is for searching globally within the string. - And the
[0]
after thematch()
method means that we're only interested in the first finding[?] (index 0).
[?]Thematch()
method produces array of found patterns.
B. Python
Let's use the same input. And activate Python power.
On the above example, the list is converted into string, by using str(a)
. Then findall()
transformed that string into list (of found patterns). And then the string to number (integer) mapping begins -- the map()
function.
For that kind of input, which has digit pattern in every string (and just number), the method will produce the exact same output as the JavaScript version.
But, for scattered around number, e.g. the number patterns for each member is separated by non-digit, and we just wanna take the first found number pattern (index 0), we can substitute the method for variable b
into this:
Or this:
Whichever the most proper one.
But, if we time the execution using timeit
module, the map()
shorthand is faster than the second one. The populating list using that for in
method. The third snippet is the slowest, since it's just the second one but then it's mapped. Like, seriously.
Anywho, be careful if you then have list member which has no digit in it -- because of the findall()
method.
Put some additional filter before using any of those snippets above if you know that your input is gonna have mixed elements.
Or use the standard looping.
.......
...
I'll be going now. Thanks for visiting.
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