Although I share the feelings of “sb” about pagination.

from pyparsing import OneOrMore
sentence = OneOrMore(word)

The definition of ‘word’ is given on the previous page:

word = Word(lowercase)

where ‘lowercase’ is imported from the ‘string’ module and equals

abcdefghijklmnopqrstuvwxyz

The definition of the BNF type ‘word’ is Word(lowercase), ie. a concatenation of any character in the string (or list, so you want) ‘lowercase’, which is a-z.

A sentence is defined as OneOrMore words.

The string ‘Hello world’ can not be parsed since it does not match OneOrMore(word): the first item in it (‘Hello’) contains characters not matching the definition of word: the ‘H’ (since we defined a word to be a concatenation of lowercase characters, it shouldn’t contain any uppercase characters).

As you can see, on page 3 a better definition of sentence is constructed using a ‘startword’ definition which should be a concatenation of one uppercase character, followed by zero or more lowercase characters.The example shows ‘A valid sentence.’ can be parsed and validated. The string ‘Hello world!’ would be valid in this BNF construct too. ‘Hello world’ would not match since we’re missing a punctuation sign.

Using the definitions from page 3

almost_valid_sentence = startword + body

or (even more limited)

hello_caps = startword + word

would validate and parse ‘Hello world’.

print sentence.parseString(‘hello world’) # notice >1 spaces
# returns ['hello', 'world']
print sentence.parseString(‘Hello world’)
# raises a ParseException

Why does the second one raise an exception ?

Regards,