pandas str字符串处理

object str

Object str is defined as a attribute of a Seires or a Index,
specifically used to handle the textual content.

s.str

Common method

s.str[n] # serial indexer

Split

s.str.split(regex, n, expand)
s.str.rsplit(regex, n, expand)

regex is a regular expression as a seperator.
n is the max num of split operations.
expand is a bool value, indicating whether expands result as many columns.

Merge

s.str.join(sep)
s1.str.cat(s2, sep, na_rep, join)

sep is a str as seperator.
na_rep is a str to replace NaN.
join is the method of joining.

Match

s.str.contains(regex) # return bool value
s.str.startswith(regex)
s.str.endswith(regex)
s.str.find(string) # return index
s.str.rfind(string)

Replace

s.str.replace(regex, value)
s.str.replace(regex, func)
s.str.replace(string, value, regex=False)

regex is a regular expression.
value is the alternate value.
func, inputs a re.Match object, outputs a string.

Extract

s.str.extract(regex) # return a df
s.str.extractall(regex)
s.str.findall(regex) # return a series

Letter processing

s.str.upper()
s.str.lower()
s.str.title()
s.str.capitalize()
s.str.swapcase()

Numeric operation

pd.to_numeric(s, errors, downcast)

s is a ps.Series.
errors is a str in [‘raise’, ‘coerce’, ‘ignore’],
indicating how to process error.
downcast is a str in [‘integer’, ‘signed’, ‘unsigned’, ‘float’].

Statistics

s.str.len()
s.str.count(regex)

Formatting

s.str.strip()
s.str.rstrip()
s.str.lstrip()
s.str.pad(num, direction, padding)

num is the min length.
direction is a string in [‘right’, ‘left’, ‘both’],
indicating the padding direction.\