How do I change the sequence of string? For e.g.
mys='4002-10-21'
Expected result:
'4002-21-10'
What I have tried:
I can enumerate the splitted string and then re-arrange the sequence like 1-3-2
newlist=list()
for i, v in enumerate(mys.split('-')):
newlist.append(v)
With operator.itemgetter you can get multiple items with a single call:
>>> from operator import itemgetter
>>> '-'.join(itemgetter(0,2,1)(mys.split('-')))
'4002-21-10'
With string format you can pick values from arguments:
>>> "{0}-{2}-{1}".format(*mys.split('-'))
'4002-21-10'
With re.sub you can capture groups and reorder them (assuming digits):
>>> import re
>>> re.sub(r'(\d+)-(\d+)-(\d+)', r'\1-\3-\2', mys)
'4002-21-10'
If you need this in pandas (as hinted in comments), you can use the regex-based approach in both DataFrame.replace and Series.str.replace, for example (add inplace=True for in-place subs):
>>> import pandas as pd
>>> df = pd.DataFrame({'dates': ['4002-10-21']})
>>> df.dates.replace(r'(\d+)-(\d+)-(\d+)', r'\1-\3-\2', regex=True)
0 4002-21-10
Name: dates, dtype: object
If you're really trying to just reformat datetime string, I suggest you parse the string to a datetime object and format it as you wish:
import datetime
def rearrange(*args):
return [datetime.datetime.strptime(arg, '%Y-%m-%d').strftime('%Y-%d-%m') for arg in args]
>>> rearrange('4002-10-21', '4002-10-28')
['4002-21-10', '4002-28-10']
Given the context of the question, your approach is fine:
mys = '4002-10-21'
parts = mys.split('-')
mys = parts[0] + '-' + parts[2] + '-' + parts[1]
print(mys) # "4002-21-10"
It's brittle certainly, but if it's for a personal or one-off script, who cares? If you need more flexibility, then you'll need to describe more explicitly the nature of your constraints.
One good way is to use regular expressions this way the numbers which I presume can have different lengths eg: '4002-21-1' will also work fine.
import re
mys = '4002-21-10'
parts = re.findall('[\d]+', mys) # finds all numbers that are next to each other
print(parts) # just so you see what is created
formatted_mys = parts[0] + "-" + parts[2] + "-" + parts[1] # put the parts together in the way you wanted
You can remove the print line if you wish of course. There are many others ways to do what you want but if you need it to be flexible this is what I would recommend.
Given:
mys='4002-10-21'
You can simply write up a function for it such as this:
def change_order(string, split_char, *args):
string = string.split(split_char)
new_list = []
for i in args:
try:
new_list.append(string[i]) # change to i-1 for abstracted parameters
except IndexError:
return False
return split_char.join(new_list)
Which given '4002-10-21' with an 1, 3, 2 (actual code takes 1 away because it's zero-indexed) reordering gives:
>>> test.change_order('4002-10-21', '-', 0, 2, 1)
'4002-21-10'
You can split on -, then re-join with - as the separator, but simply re-order as you need to:
>>> s = '4002-10-21'
>>> d = s.split('-')
>>> new_s = "-".join((d[0], d[2], d[1]))
'4002-21-10'
Or, without join, after you split, you can simply do:
new_s = "{}-{}-{}".format(d[0], d[2], d[1])
You can try this:
mys='4002-10-21'
m = mys.split("-")
new_mys = m[0]+"-"+'-'.join(m[1:][::-1])
Output:
'4002-21-10'
L='4002-10-21'
L=L.split("-")
L[i:3] = L[2:0:-1]
"-".join(L)
You could use slices.
yyyy-mm-ddtoyyyy-dd-mm?pandas. Please see my updated answer below, hope it helps you.