numarray Manual

11.4 Character array methods

CharArray object has these public methods:

tolist( ): tolist() returns a nested list of strings corresponding to all the elements in the array.

copy( ): copy() returns a deep copy of the character array.

raw( )

raw() returns the corresponding RawCharArray view.

     >>> c=str.array(["this","that","another"])
     >>> c.raw()
     RawCharArray(['this   ', 'that   ', 'another'])

resized( n, fill=' ')

resized(n) returns a copy of the array, resized so that each element is of length n characters. Extra characters are filled with value fill. Caution: do not confuse this method with resize() which changes the number of elements rather than the size of each element.

     >>> c = str.array(["this","that","another"])
     >>> c.itemsize()
     7
     >>> d = c.resized(20)
     >>> print d
     ['this', 'that', 'another']
     >>> d.itemsize()
     20

concatenate( other)

concatenate(other) returns a new array which corresponds to the element by element concatenation of other to self. The addition operator is also overloaded to perform concatenation.

     >>> print map(str, range(3)) + array(["this","that","another one"])
     ['0this', '1that', '2another one']
     >>> print "prefix with trailing whitespace   " + array(["."])
     ['prefix with trailing whitespace   .']

sort( )

sort modifies the CharArray inplace so that its elements are in sorted order. sort only works for 1D character arrays. Like the sort() for the Python list, CharArray.sort() returns nothing.

     >>> a=str.array(["other","this","that","another"])
     >>> a.sort()
     >>> print a
     ['another', 'other', 'that', 'this']

argsort( )

argsort returns a numarray corresponding to the permutation which will put the character array self into sorted order. argsort only works for 1D character arrays.

     >>> a=str.array(["other","that","this","another"])
     >>> a.argsort()
     array([3, 0, 1, 2])
     >>> print a[ a.argsort ] 
     ['another', 'other', 'that', 'this']

amap( f): amap applies the function f to every element of self and returns the nested list of the results. The function f should operate on a single string and may return any Python value.

     >>> c = str.array(['this','that','another'])
     >>> print c.amap(lambda x: x[-2:])
     ['is', 'at', 'er']

match( pattern, flags=0)

match uses Python regular expression matching over all elements of a character array and returns a tuple of numarrays corresponding to the indices of self where the pattern matches. flags are passed directly to the Python pattern matcher defined in the re module of the standard library.

     >>> a=str.array([["wo","what"],["wen","erewh"]])
     >>> print a.match("wh[aebd]")
     (array([0]), array([1]))
     >>> print a[ a.match("wh[aebd]") ]
     ['what']

search( pattern,flags=0): search uses Python regular expression searching over all elements of a character array and returns a tuple of numarrays corresponding to the indices of self where the pattern was found. flags are passed directly to the Python pattern search method defined in the re module of the standard library. flags should be an or'ed combination (use the $\vert$ operator) of the following re variables: IGNORECASE, LOCALE, MULTILINE, DOTALL, VERBOSE. See the re module documentation for more details.

sub( pattern,replacement,flags=0,count=0)

sub performs Python regular expression pattern substitution to all elements of a character array. flags and count work as they do for re.sub().

     >>> a=str.array([["who","what"],["when","where"]])
     >>> print a.sub("wh", "ph")
     [['pho', 'phat'],
      ['phen', 'phere']])

grep( pattern, flags=0)

grep is intended to be used interactively to search a CharArray for the array of strings which match the given pattern. pattern should be a Python regular expression (see the re module in the Python standard library, which can be as simple as a string constant as shown below.

     >>> a=str.array([["who","what"],["when","where"]])
     >>> print a.grep("whe")
     ['when', 'where']

eval( )

eval executes the Python eval function on each element of a character array and returns the resulting numarray. eval is intended for use converting character arrays to the corresponding numeric arrays. An exception is raised if any string element fails to evaluate.

     >>> print str.array([["1","2"],["3","4."]]).eval()
     [[1., 2.],
      [3., 4.]]

maxLen( )

maxLen returns the minimum element length required to store the stripped elements of the array self.

     >>> print str.array(["this","there"], itemsize=20).maxLen()
     5

truncated( )

truncated returns an array corresponding to self resized so that it uses a minimum amount of storage.

     >>> a = str.array(["this  ","that"])
     >>> print a.itemsize()
     6
     >>> print a.truncated().itemsize()
     4

count( s)

count counts the occurences of string s in array self.

     >>> print array(["this","that","another","this"]).count("this")
     2

info( ): This will display key attributes of the character array.

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