CODEWITHSUNDEEP
pythonarraysstring
sc28
sc28

Reputation: 1213

Python: rearranging an array of strings

I'm trying to rearrange the following array of strings:

myString =['000', ['1', 'two', 'three'], ['1', 'b', 'c']]

So that myString2 looks like

myString2 = [['000', '1', 'two', 'three'], [['000', '1', 'b', 'c']]

Looking around for some ideas (e.g. here) I attempted the following loop:

myString2 = []
for i in range(0,len(myString)-1):
    myString2 [i].append(myString[0])
    myString2 [i].append(myString[i])

But I get an error which I don't really understand :

IndexError: list index out of range

I'm fairly new to python and wonder if there is perhaps a simpler way than my current idea, and if not, if someone could kindly explain what is preventing the loop from running.

Upvotes: 0

Views: 192

Answers (3)

hansaplast
hansaplast

Reputation: 11573

You were close with your script, this works:

myString =['000', ['1', 'two', 'three'], ['1', 'b', 'c']]
myString2 = []
for i in range(1,len(myString)):
    myString2.append(myString[0])
    myString2.append(myString[i])

What was wrong?

  • myString2[i].append attempts to append something at myString, index i, so at first iteration it tries to access myString[0] but myString is still empty, that causes the out of range error. Instead use append just on the list and it will add the element at the last position
  • you need to loop from the second element range(1,...
  • range is exclusive, so a range(1,5) is [1,2,3,4] -> you don't need to substract 1

Upvotes: 2

Chris
Chris

Reputation: 22953

Instead of trying to use the first list to hold the string 0000, why not put it in a constant instead

MAGIC_STRING = '0000'

and then simply use the constant to create the new, modified sublists:

myString = [['1', 'two', 'three'], ['1', 'b', 'c']]
myString2 = [[MAGIC_STRING] + el for el in myString]

Upvotes: 0

Jean-François Fabre
Jean-François Fabre

Reputation: 140186

The snippet of code you provided cannot work because of variable names, so I won't try to explain you what's wrong with it further.

That said, those problems can be easily done in one-liners using list comprehensions:

myString =['000', ['1', 'two', 'three'], ['1', 'b', 'c']]

new_string = [[myString[0]]+s for s in myString[1:]]

print(new_string)

just create a new list of lists, with the first element as head, and the rest as tail.

Results as:

[['000', '1', 'two', 'three'], ['000', '1', 'b', 'c']]

Upvotes: 1

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