8.9 Splitting and Joining Strings

  • Tokens typically are separated by whitespace characters such as blank, tab and newline, though other characters may be used—the separators are known as delimiters

Splitting Strings

  • To tokenize a string at a custom delimiter, specify the delimiter string that split uses to tokenize the string
In [1]:
letters = 'A, B, C, D'
In [2]:
letters.split(', ')
Out[2]:
['A', 'B', 'C', 'D']
  • Specify the maximum number of splits with an integer as the second argument
  • Last token is the remainder of the string
In [3]:
letters.split(', ', 2)
Out[3]:
['A', 'B', 'C, D']
  • rsplit performs the same task as split but processes the maximum number of splits from the end of the string toward the beginning

Joining Strings

  • join concatenates the strings in its argument, which must be an iterable containing only string values
  • The separator between the concatenated items is the string on which you call join
In [4]:
letters_list = ['A', 'B', 'C', 'D']
In [5]:
','.join(letters_list)
Out[5]:
'A,B,C,D'
  • Join the results of a list comprehension that creates a list of strings
In [6]:
','.join([str(i) for i in range(10)])
Out[6]:
'0,1,2,3,4,5,6,7,8,9'

String Methods partition and rpartition

String method partition splits a string into a tuple of three strings based on the method’s separator argument

  • the part of the original string before the separator
  • the separator itself
  • the part of the string after the separator
In [7]:
'Amanda: 89, 97, 92'.partition(': ')
Out[7]:
('Amanda', ': ', '89, 97, 92')
  • To search for the separator from the end of the string, use method rpartition
In [8]:
url = 'http://www.deitel.com/books/PyCDS/table_of_contents.html'
In [9]:
rest_of_url, separator, document = url.rpartition('/')
In [10]:
document
Out[10]:
'table_of_contents.html'
In [11]:
rest_of_url
Out[11]:
'http://www.deitel.com/books/PyCDS'

String Method splitlines

  • splitlines returns a list of new strings representing lines of text split at each newline character in the original string
In [12]:
lines = """This is line 1
This is line2
This is line3"""
In [13]:
lines
Out[13]:
'This is line 1\nThis is line2\nThis is line3'
In [14]:
lines.splitlines()
Out[14]:
['This is line 1', 'This is line2', 'This is line3']
  • Passing True to splitlines keeps the newlines
In [15]:
lines.splitlines(True)
Out[15]:
['This is line 1\n', 'This is line2\n', 'This is line3']

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