Similar function in C++ to Python's strip()?

Question

There is a very useful function in Python called strip(). Any similar ones in C++?

http://stackoverflow.com/questions/352055/best-algorithm-to-strip-leading-and-trailing-spaces-in-c — Veger, Feb 20 '12 at 09:28
possible duplicate of [What's the best way to trim std::string](http://stackoverflow.com/questions/216823/whats-the-best-way-to-trim-stdstring) — David Heffernan, Feb 20 '12 at 09:36
possible duplicate of [Python strip a string](http://stackoverflow.com/questions/1038824/python-strip-a-string) — Marcin, Feb 20 '12 at 09:36
possible duplicate of [Mimic Python's strip() function in C](http://stackoverflow.com/questions/1488372/mimic-pythons-strip-function-in-c) — Lazik, Jul 07 '15 at 19:00
[`boost::trim`](https://www.boost.org/doc/libs/1_43_0/doc/html/boost/algorithm/trim.html) — sp2danny, Sep 09 '21 at 09:37

score 8 · Answer 1 · answered Jan 27 '21 at 14:03

8

I use this:

#include <string>
#include <cctype>

std::string strip(const std::string &inpt)
{
    auto start_it = inpt.begin();
    auto end_it = inpt.rbegin();
    while (std::isspace(*start_it))
        ++start_it;
    while (std::isspace(*end_it))
        ++end_it;
    return std::string(start_it, end_it.base());
}

answered Jan 27 '21 at 14:03

Ferdi Kedef

126
1
3

If inpt="\t", then the last step will throw "string too long" exception. – xycs Mar 24 '22 at 18:57
A safer version is provided below. – xycs Mar 24 '22 at 19:38

score 7 · Accepted Answer · answered Feb 20 '12 at 10:06

There's nothing built-in; I used to use something like the following:

template <std::ctype_base::mask mask>
class IsNot
{
    std::locale myLocale;       // To ensure lifetime of facet...
    std::ctype<char> const* myCType;
public:
    IsNot( std::locale const& l = std::locale() )
        : myLocale( l )
        , myCType( &std::use_facet<std::ctype<char> >( l ) )
    {
    }
    bool operator()( char ch ) const
    {
        return ! myCType->is( mask, ch );
    }
};

typedef IsNot<std::ctype_base::space> IsNotSpace;

std::string
trim( std::string const& original )
{
    std::string::const_iterator right = std::find_if( original.rbegin(), original.rend(), IsNotSpace() ).base();
    std::string::const_iterator left = std::find_if(original.begin(), right, IsNotSpace() );
    return std::string( left, right );
}

which works pretty well. (I now have a significantly more complex version which handles UTF-8 correctly.)

score 1 · Answer 3 · edited Sep 09 '21 at 09:21

1

void strip(std::string &str)
{
    if  (str.length() != 0)
    {
    auto w = std::string(" ") ;
    auto n = std::string("\n") ;
    auto r = std::string("\t") ;
    auto t = std::string("\r") ;
    auto v = std::string(1 ,str.front()); 
    while((v == w) || (v==t) || (v==r) || (v==n))
    {
        str.erase(str.begin());
        v = std::string(1 ,str.front());
    }
    v = std::string(1 , str.back()); 
    while((v ==w) || (v==t) || (v==r) || (v==n))
    {
        str.erase(str.end() - 1 );
        v = std::string(1 , str.back());
    }
}

edited Sep 09 '21 at 09:21

Hybr13

80
2
12

answered Sep 25 '19 at 02:50

Mhadhbi issam

197
3
6

1

it work with me good , it is not well optimized but it do the job correctly . i made it void to use it in for_each algorithm . – Mhadhbi issam Sep 25 '19 at 02:52

score 0 · Answer 4 · answered Mar 24 '22 at 19:37

This is on top of the answer provided by Ferdi Kedef to make it safer.

void strip(std::string& str)
{
    if (str.length() == 0) {
        return;
    }

    auto start_it = str.begin();
    auto end_it = str.rbegin();
    while (std::isspace(*start_it)) {
        ++start_it;
        if (start_it == str.end()) break;
    }
    while (std::isspace(*end_it)) {
        ++end_it;
        if (end_it == str.rend()) break;
    }
    int start_pos = start_it - str.begin();
    int end_pos = end_it.base() - str.begin();
    str = start_pos <= end_pos ? std::string(start_it, end_it.base()) : "";
}

Similar function in C++ to Python's strip()?

4 Answers4

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