Replace substring# replace all characters "a" with "x"
"a1 a2 a3 a4".replace("a","x") x1 x2 x3 x4 replace file ending ".txt" with ".csv"
mydata.csv
remove file ending ".txt"
mydata
Split and merge text strings split >>> 'a1,a2,a3'.split(',') ['a1', 'a2', 'a3'] get filename (get first list element)
>>> 'filename.txt.bz2'.split('.')[0] 'filename' split() by default used all whitespace characters (space, tab \t, new line \n, \r, ...)join - to concatenate a list to a string
>>> ','.join(['a1', 'a2', 'a3']) # comma separated'a1,a2,a3' >>> ' '.join(['a1', 'a2', 'a3']) # space separated'a1 a2 a3' concatenate strings
>>> 'hello' + ' ' + 'world' 'hello world' for many strings, better use join()
>>> ''.join(['hello','world']) 'helloworld' >>> ' '.join(['hello','world']) 'hello world' # add prefix, only if not already present
s = 'hello world' prefix = 'hello' if not s.startswith(prefix): s = prefix + ' ' + s 'hello world'
length of string
>>> len('hello') 5 sorted list
>>> sorted(['C', 'b', 'd','A'], key=str.lower) ['A', 'b', 'C', 'd'] sort list in descending order >>> sorted([4, 1, 3, 2], reverse=True) [4, 3, 2, 1] convert strings to numbers (and back as string) >>> int('23') 23 >>> float('23.1') 23.1 >>> str(23) '23' see also: format() format('hello','>20') ' hello' convert all strings in a list into int numbers
s = ['4', '1', '3', '2'] n = [int(x) for x in s] [4, 1, 3, 2] see also: List Comprehension
check for substring
>>> 'day' in 'Friday' True get index location of substring
'Friday'.index('day') 3 s='hello' [idx for idx, letter in enumerate(s) if letter == 'l'] [2, 3] find a substring in list items
>>> dates = ['May 2015','January 2012','Dezember 2015','June 2014'] >>> dates2015= [s for s in dates if '2015' in s] ['May 2015', 'Dezember 2015'] check if any substring is present in list items
print('yes, 2015 is present') read more: |