4.1 Standard Module string

 

This module defines some constants useful for checking character classes and some useful string functions. See the module re  for string functions based on regular expressions.

The constants defined in this module are are:

digits

The string '0123456789'.

hexdigits

The string '0123456789abcdefABCDEF'.

letters

The concatenation of the strings lowercase() and uppercase() described below.

lowercase

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.

octdigits

The string '01234567'.

uppercase

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

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 functions defined in this module are:

atof (s)

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 "-"). Note that this behaves identical to the built-in function float()  when passed a string.

atoi (s[, base])

Convert string s to an integer in the given base. The string must consist of one or more digits, optionally preceded by a sign ("+" or "-"). The base defaults to 10. If it is 0, a default base is chosen depending on the leading characters of the string (after stripping the sign): "0x" or "0X" means 16, "0" means 8, anything else means 10. If base is 16, a leading "0x" or "0X" is always accepted. Note that when invoked without base or with base set to 10, this behaves identical to the built-in function int() when passed a string. (Also note: for a more flexible interpretation of numeric literals, use the built-in function eval() .)

atol (s[, base])

Convert string s to a long integer in the given base. The string must consist of one or more digits, optionally preceded by a sign ("+" or "-"). The base argument has the same meaning as for atoi(). A trailing "l" or "L" is not allowed, except if the base is 0. Note that when invoked without base or with base set to 10, this behaves identical to the built-in function long()  when passed a string.

capitalize (word)

Capitalize the first character of the argument.

capwords (s)

Split the argument into words using split(), capitalize each word using capitalize(), and join the capitalized words using join(). Note that this replaces runs of whitespace characters by a single space, and removes leading and trailing whitespace.

expandtabs (s, tabsize)

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[, start[,end]])

Return the lowest index in s where the substring sub is found such that sub is wholly contained in s[start:end]. Return -1 on failure. Defaults for start and end and interpretation of negative values is the same as for slices.

rfind (s, sub[, start[, end]])

Like find() but find the highest index.

index (s, sub[, start[, end]])

Like find() but raise ValueError when the substring is not found.

rindex (s, sub[, start[, end]])

Like rfind() but raise ValueError when the substring is not found.

count (s, sub[, start[, end]])

Return the number of (non-overlapping) occurrences of substring sub in string s[start:end]. Defaults for start and end and interpretation of negative values is the same as for slices.

lower (s)

Convert letters to lower case.

maketrans (from, to)

Return a translation table suitable for passing to translate() or regex.compile(), that will map each character in from into the character at the same position in to; from and to must have the same length.

split (s[, sep[, maxsplit]])

Return a list of the words of the string s. If the optional second argument sep is absent or None, the words are separated by arbitrary strings of whitespace characters (space, tab, newline, return, formfeed). If the second argument sep is present and not None, it specifies a string to be used as the word separator. The returned list will then have one more items than the number of non-overlapping occurrences of the separator in the string. The optional third argument maxsplit defaults to 0. If it is nonzero, at most maxsplit number of splits occur, and the remainder of the string is returned as the final element of the list (thus, the list will have at most maxsplit+1 elements).

splitfields (s[, sep[, maxsplit]])

This function behaves identically to split(). (In the past, split() was only used with one argument, while splitfields() was only used with two arguments.)

join (words[, sep])

Concatenate a list or tuple of words with intervening occurrences of sep. The default value for sep is a single space character. It is always true that "string.join(string.split(s, sep), sep)" equals s.

joinfields (words[, sep])

This function behaves identical to join(). (In the past, join() was only used with one argument, while joinfields() was only used with two arguments.)

lstrip (s)

Remove leading whitespace from the string s.

rstrip (s)

Remove trailing whitespace from the string s.

strip (s)

Remove leading and trailing whitespace from the string s.

swapcase (s)

Convert lower case letters to upper case and vice versa.

translate (s, table[, deletechars])

Delete all characters from s that are in deletechars (if present), and then translate the characters using table, which must be a 256-character string giving the translation for each character value, indexed by its ordinal.

upper (s)

Convert letters to upper case.

ljust (s, width)

rjust (s, width)

center (s, width)

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)

Pad a numeric string on the left with zero digits until the given width is reached. Strings starting with a sign are handled correctly.

replace (str, old, new[, maxsplit])

Return a copy of string str with all occurrences of substring old replaced by new. If the optional argument maxsplit is given, the first maxsplit occurrences are replaced.

This module is implemented in Python. Much of its functionality has been reimplemented in the built-in module strop . However, you should never import the latter module directly. When string discovers that strop exists, it transparently replaces parts of itself with the implementation from strop. After initialization, there is no overhead in using string instead of strop.