4.5. Standard Module `string`

This module defines some constants useful for checking character classes, some exceptions, and some useful string functions. The constants are:

letters -- data of module string: The concatenation of the strings lowercase and uppercase described below.

lowercase -- data of module string: A string containing all the characters that are considered lowercase letters. On most systems this is the string 'abcdefghijklmnopqrstuvwxyz'. Do not change its definition -- the effect on the routines upper and swapcase is undefined.

uppercase -- data of module string: A string containing all the characters that are considered uppercase letters. On most systems this is the string 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'. Do not change its definition -- the effect on the routines lower and swapcase is undefined.

whitespace -- data of module string: A string containing all characters that are considered whitespace. On most systems this includes the characters space, tab, linefeed, return, formfeed, and vertical tab. Do not change its definition -- the effect on the routines strip and split is undefined.

The exceptions are:

atof_error -- exception of module string: Exception raised by atof when a non-float string argument is detected. The exception argument is the offending string.

atoi_error -- exception of module string: Exception raised by atoi when a non-integer string argument is detected. The exception argument is the offending string.

atol_error -- exception of module string: Exception raised by atol when a non-integer string argument is detected. The exception argument is the offending string.

index_error -- exception of module string: Exception raised by index when sub is not found. The exception argument is undefined (it may be a tuple containing the offending arguments to index or it may be the constant string 'substring not found').

The functions are:

atof (s) -- function of module string: Convert a string to a floating point number. The string must have the standard syntax for a floating point literal in Python, optionally preceded by a sign (`+' or `-').

atoi (s) -- function of module string: Convert a string to an integer. The string must consist of one or more digits, optionally preceded by a sign (`+' or `-').

atol (s) -- function of module string: Convert a string to a long integer. The string must consist of one or more digits, optionally preceded by a sign (`+' or `-').

expandtabs (s, tabsize) -- function of module string: Expand tabs in a string, i.e. replace them by one or more spaces, depending on the current column and the given tab size. The column number is reset to zero after each newline occurring in the string. This doesn't understand other non-printing characters or escape sequences.

find (s, sub, i) -- function of module string: Return the lowest index in s not smaller than i where the substring sub is found. Return -1 when sub does not occur as a substring of s with index at least i. If i is omitted, it defaults to 0. If i is negative, len(s) is added.

rfind (s, sub, i) -- function of module string: Like find but finds the highest index.

index (s, sub, i) -- function of module string: Like find but raise index_error when the substring is not found.

rindex (s, sub, i) -- function of module string: Like rfind but raise index_error when the substring is not found.

split (s) -- function of module string: Returns a list of the whitespace-delimited words of the string s.

splitfields (s, sep) -- function of module string: Returns a list containing the fields of the string s, using the string sep as a separator. The list will have one more items than the number of non-overlapping occurrences of the separator in the string. Thus, string.splitfields(s, ' ') is not the same as string.split(s), as the latter only returns non-empty words. As a special case, splitfields(s, '') returns [s], for any string s. (See also regsub.split().)

join (words) -- function of module string: Concatenate a list or tuple of words with intervening spaces.

joinfields (words, sep) -- function of module string: Concatenate a list or tuple of words with intervening separators. It is always true that string.joinfields(string.splitfields(t, sep), sep) equals t.

strip (s) -- function of module string: Removes leading and trailing whitespace from the string s.

swapcase (s) -- function of module string: Converts lower case letters to upper case and vice versa.

center (s, width) -- function of module string: These functions respectively left-justify, right-justify and center a string in a field of given width. They return a string that is at least width characters wide, created by padding the string s with spaces until the given width on the right, left or both sides. The string is never truncated.

zfill (s, width) -- function of module string: Pad a numeric string on the left with zero digits until the given width is reached. Strings starting with a sign are handled correctly.

4.5. Standard Module string