Python range and strings

How to Iterate over a String in Python

In this tutorial, you will find out different ways to iterate strings in Python. You could use a for loop, range in Python, a slicing operator, and a few more methods to traverse the characters in a string.

Multiple Ways to Iterate Strings in Python

The following are various ways to iterate the chars in a Python string. Let’s first begin with the for loop method.

Using for loop to traverse a string

It is the most prominent and straightforward technique to iterate strings. Follow the below sample code:

""" Python Program: Using for loop to iterate over a string in Python """ string_to_iterate = "Data Science" for char in string_to_iterate: print(char)

The result of the above coding snippet is as follows:

Python range to iterate over a string

Another quite simple way to traverse the string is by using the Python range function. This method lets us access string elements using the index.

""" Python Program: Using range() to iterate over a string in Python """ string_to_iterate = "Data Science" for char_index in range(len(string_to_iterate)): print(string_to_iterate[char_index])

The result of the above coding snippet is as follows:

How to use the slice operator to iterate strings partially

You can traverse a string as a substring by using the Python slice operator ([]). It cuts off a substring from the original string and we can iterate over it partially.

# Slicing Operator string [starting index : ending index : step value]

To use this method, provide the starting and ending indices along with a step value and then traverse the string. Below is the example code that iterates over the first six letters of a string.

""" Python Program: Using slice [] operator to iterate over a string partially """ string_to_iterate = "Python Data Science" for char in string_to_iterate[0 : 6 : 1]: print(char)

The result of the above coding snippet is as follows:

You can take the slice operator usage further by using it to iterate over a string but leaving every alternate character. Check out the below example:

""" Python Program: Using slice [] operator to iterate over a specific parts of a string """ string_to_iterate = "Python_Data_Science" for char in string_to_iterate[ : : 2]: print(char)

The result of the above coding snippet is as follows:

Traverse string backward using the slice operator

If you pass a -ve step value and skip the starting as well as ending indices, then you can iterate in the backward direction. Go through the given code sample.

«»» Python Program: Using slice [] operator to iterate string backward «»» string_to_iterate = «Machine Learning» for char in string_to_iterate[ : : -1]: print(char)

The result of the above coding snippet is as follows:

g n i n r a e L e n i h c a M

Using indexing to iterate strings backward

The slice operator first generates a reversed string, and then we use the for loop to traverse it. Instead of doing it, we can use the indexing to iterate strings backward.

«»» Python Program: Using indexing to iterate string backward «»» string_to_iterate = «Machine Learning» char_index = len(string_to_iterate) — 1 while char_index >= 0: print(string_to_iterate[char_index]) char_index -= 1

The result of the above coding snippet is as follows:

g n i n r a e L e n i h c a M

Alternatively, we can pass the -ve index value and traverse the string backward. See the below example.

""" Python Program: Using -ve index to iterate string backward """ string_to_iterate = "Learn Python" char_index = 1 while char_index 
The result of the above coding snippet is as follows:
Summary – Program to iterate strings char by char
Let’s now consolidate all examples inside the Main() function and execute from there.
""" Program: Python Program to iterate strings char by char """ def Main(): string_to_iterate = "Data Science" for char in string_to_iterate: print(char) string_to_iterate = "Data Science" for char_index in range(len(string_to_iterate)): print(string_to_iterate[char_index]) string_to_iterate = "Python Data Science" for char in string_to_iterate[0 : 6 : 1]: print(char) string_to_iterate = "Python_Data_Science" for char in string_to_iterate[ : : 2]: print(char) string_to_iterate = "Machine Learning" for char in string_to_iterate[ : : -1]: print(char) string_to_iterate = "Machine Learning" char_index = len(string_to_iterate) - 1 while char_index >= 0: print(string_to_iterate[char_index]) char_index -= 1 string_to_iterate = "Learn Python" char_index = 1 while char_index 
The result of the above coding snippet is as follows:
D a t a S c i e n c e D a t a S c i e n c e P y t h o n P t o _ a a S i n e g n i n r a e L e n i h c a M g n i n r a e L e n i h c a M n o h t y P n r a e L
 
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python range and string
 
I am trying to define a function CountXSeconds which for a given integer value X will create a string explaining what you need to say out loud when counting seconds. e.g. CountXSeconds(3) should give the output “1 one thousand. 2 one thousand. 3 one thousand” This is the closest I got but I can't find a way to include the string "one thousand" without errors:
 
def main(): CountXSeconds() def CountXSeconds(): n = int(input("What is your number?" )) if n >= 1: print(*range(1,n+1)) if __name__ == "__main__": main() 
 
Do you want the string to print just "One one thousand", the common thing to say when counting seconds to get the length right. Or do you want it to print how to say eg. 1234 ? One thousand two hundred thirty four.
 
Can you please give me the name and phone number of the person who taught you this style so I can call them and inform them that Python is not C/C++?
 
Lol erm you'll have to excuse me i am still trying to learn Python! its a complete alien experience for me
 
3 Answers 3
 
for i in range(0,n): print(i,"one thousand.",end='') print() 
 
Here's a solution that solves your problem but is code-golfed enough to look weird as a homework answer at this level:
 
print(' '.join(map(lambda x: "%d one thousand." % x, range(1, n)))) 
 
 
A "lambda function" is simply a very small way of writing a function without naming it. In this case, lambda x: "%d one thousand." % x will take in a number x and output the string "1 one thousand" if x=1, for example.
 
The % operator used in that lambda is a shortcut for string.format. That's a bit too much to explain right now, but here it basically means "insert the value of x where the %d is".
 
The map function is a fancy way of writing an entire for loop in a single line. It takes a function and a list, and applies the function to each item in the list.
 
' '.join is a peculiarity of Python. What it does is take a list and turn it into a string by putting a space between each of the items. You would think that it'd be a function you call on the list, but in Python it's a function on the string instead.
 
 
Here's a much more clearly written version:
 
numbers = range(1, n) make_count_string = lambda x: "%d one thousand." % x count_strings = map(make_count_string, numbers) combined_string = ' '.join(count_strings) print(combined_string) 
 
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