STRINGS
LOVE IT !! Besides numbers, Python can also manipulate strings, which can be expressed in several ways.
#! python works with strings
# Used 1 to 24 in printing to see the results in console.
# Strings can be concatenated (glued together) with the + operator, and repeated with *:
word = 'Help' + 'A'
print 1,word
print 2,'<' + word*5 + '>'
# Two string literals next to each other are automatically concatenated;
# the first line above could also have been written "word = 'Help' 'A'";
# this only works with two literals, not with arbitrary string expressions:
st='str' 'ing' # <- This is ok
print 3, st
st='str'.strip() + 'ing' # <- This is ok
print 4, st
# Strings can be subscripted (indexed); like in C, the first character of a string
# has subscript (index) 0. There is no separate character type; a character is
# simply a string of size one. Like in Icon, substrings can be specified with
# the slice notation: two indices separated by a colon.
print 5, word[4]
print 6, word[0:2]
print 7, word[2:4]
# Slice indices have useful defaults; an omitted first index defaults to zero,
# an omitted second index defaults to the size of the string being sliced.
print 8, word[:2] # The first two characters
print 9, word[2:] # All but the first two characters
# Python strings cannot be changed. Assigning to an indexed position in the string results in an error:
# However, creating a new string with the combined content is easy and efficient:
print 10, 'x' + word[1:]
print 11, 'Splat' + word[4]
# Here's a useful invariant of slice operations: s[:i] + s[i:] equals s.
print 12, word[:2] + word[2:]
print 13, word[:3] + word[3:]
# Degenerate slice indices are handled gracefully: an index that is too large is replaced
# by the string size, an upper bound smaller than the lower bound returns an empty string.
print 14, word[1:100]
print 15, word[10:]
print 16, word[2:1]
# Indices may be negative numbers, to start counting from the right. For example:
print 17, word[-1] # The last character
print 18, word[-2] # The last-but-one character
print 19, word[-2:] # The last two characters
print 20, word[:-2] # All but the last two characters
# But note that -0 is really the same as 0, so it does not count from the right!
print 21, word[-0] # (since -0 equals 0)
# Out-of-range negative slice indices are truncated, but don't try this for single-element (non-slice) indices:
print 22, word[-100:]
# print word[-10] # error
#The best way to remember how slices work is to think of the indices as pointing between characters,
#with the left edge of the first character numbered 0. Then the right edge of the last character
#of a string of n characters has index n, for example:
# +---+---+---+---+---+
# | H | e | l | p | A |
# +---+---+---+---+---+
# 0 1 2 3 4 5
#-5 -4 -3 -2 -1
s = 'supercalifragilisticexpialidocious'
print 23, s
print 24, 'length of above string is : ', len(s)
# http://www.codeskulptor.org/#user22_0UcuKWvNvVDJS7H.py
Output :
1 HelpA 2 <HelpAHelpAHelpAHelpAHelpA> 3 string 4 string 5 A 6 He 7 lp 8 He 9 lpA 10 xelpA 11 SplatA 12 HelpA 13 HelpA 14 elpA 15 16 17 A 18 p 19 pA 20 Hel 21 H 22 HelpA 23 supercalifragilisticexpialidocious 24 length of above string is : 34
