Python-如何将字符串的特定部分插入另一个字符串的特定部分

Question

I was wondering how to take a string and cut off one part of it and put that part into the beginning of another string

for example:

string1 = 'abcdefg'
string2 = 'gfedcba

How could I take the first four letters of string one and put them at the beginning of string2 so it looks like this:

string1 = 'efg'
string2 = 'abcdgfedcba'

Answer 1

You need to look into Cutting and slicing strings in Python . You will be able to solve this problem once you go through this tutorial.

SPOILERS BELOW

If your still stuck, here is a basic example to get you started:

>>> string1 = 'abcdefg'
>>> string2 = 'gfedcba'
>>> string2 = string1[:4] + string2  # prepend first four characters from string1
>>> string2
'abcdgfedcba'
>>> string1 = string1[4:] # update string1 to not keep first four characters
>>> string1
'efg'

In the above, [:4] returns everything up to, but not including, the character at position 4. Additionally, [4:] will return every character after and including position 4.

Answer 2

li = [0,1,2,3,4]
li[start:end:step]
eg. li=[2,4,5,7]
Now, i want to grab [1,2,3] from this list I can do that by using slicing

new_li=li[1:4]
print(new_li)
[1,2,3]

Similarly the indexing of strings also start from 0

string1 = 'abcdefg'
string2 = 'gfedcba'
string2 = string1[0:4] + string2 #concat 
string1 = string1[4:7]   #slice from index 4 to 7