Iterate over all characters
Since a character can be accessed by index, you can use a variable loop to iterate over all characters, which will take on possible index values. For example, a program that displays all the character codes of the string
s would look like this
for i in range(len(s)):
print(s[i], ord(s[i]))
Explanations for the program:
1) The
len(s) function finds the length of a string. The index of the first character is 0 and the index of the last is len(s)-1. The loop variable
i will just take values sequentially from
0 to
len(s)-1.
2) In each line, the symbol itself will be displayed first, and then its code, which is returned by the built-in function
ord().
The same enumeration can be written shorter:
for c in s:
print(c, ord(c))
In this fragment, the loop header loops through all the characters s, placing them in turn in the variable
c.
As already mentioned, the peculiarity of Python when working with strings is that strings are immutable objects. In other words, we cannot change individual characters of a string.
For example, the following statement will not work
s[5]='a'
But you can compose a new line from the characters with the required changes.
Task
In the input string, replace all characters 'a' to characters 'b'.
s = input()
sNew = ""
for c in s:
if c == 'a': c = 'b'
sNew += c
print(sNew)
In this program, the loop goes through all the characters of the string s. In the body of the loop, we check the value of the variable
с: if the symbol matches the symbol '
a', then we replace it with '
b< /code>' and add it to the end of the new line sNew using the addition operator.
This option is rather slow.
In the future, we'll take a look at the built-in string manipulation functions and learn how to do it faster.