Problem Formulation

Given a string in the octal form:

s = '0o77'

# or s = '77'

How to convert the octal string to an integer in Python?

For example, you want to convert the octal string 'o10' to the decimal integer 8.

Here are a few other examples:

Oct String to Integer using int() with Base 8

To convert an octal string to an integer, pass the string as a first argument into Python’s built-in int() function. Use base=8 as a second argument of the int() function to specify that the given string is an octal number. The int() function will then convert the octal string to an integer with base 10 and return the result.

Here’s a minimal example:

>>> int('0o77', base=8)

63

Examples

And here’s how you can convert the additional examples shown above:

>>> int('0o0', base=8)

0

>>> int('0o4', base=8)

4

>>> int('0o10', base=8)

8

>>> int('0o14', base=8)

12

>>> int('0o20', base=8)

16

>>> int('0o77', base=8)

63

>>> int('0o77777', base=8)

32767

You actually don’t need to use the prefix '0o' because your second argument already defines unambiguously that the given string is an octal number:

>>> int('0', base=8)

0

>>> int('4', base=8)

4

>>> int('10', base=8)

8

>>> int('14', base=8)

12

>>> int('20', base=8)

16

>>> int('77', base=8)

63

>>> int('77777', base=8)

32767

However, skipping the base but leaving the prefix raises a ValueError: invalid literal for int() with base 10: '0o77':

>>> int('0o77')

Traceback (most recent call last): File "<pyshell#16>", line 1, in <module> int('0o77')

ValueError: invalid literal for int() with base 10: '0o77'

It assumes that the input string is in base 10 when in fact, it isn’t.

Note: Even though passing a prefixed string '0o...' into the int() function is unambiguous, Python’s int() function doesn’t accept it if you don’t also define the base. This may be fixed in future versions!

In fact, you can specify the base argument as 0 to switch on base guessing—which should be the default behavior anyway!

Base Guessing

You can pass a prefixed string '0o...' into the int() function and set the base to 0 to switch on base guessing in Python. This uses the prefix to determine the base automatically—without you needing to set it to 16. Yet, you still have to set it to 0 so the benefit is marginal in practice.

>>> int('0o7', base=8)

7

>>> int('0o7', base=0)

7

>>> int('0o7', 0)

7

Converting Octal Literals to Int

If you don’t have an octal string but a octal number—called a literal—such as 0xff, you don’t even need the int() function because Python will automatically convert it to a decimal number:

>>> 0o743

483

>>> 0o7

7

>>> 0o10

8

Background int()

Syntax: int(value [, base]) – > int

Do you still need more background information about Python’s built-in int() function? No problem, read over the related tutorial.

Related Tutorial: Python’s Built-in int() Function

Summary: Use "given string".split('-') to split the given string by hyphen and store each word as an individual item in a list. Some other ways to split using hyphen include using a list comprehension and the regex library.

Minimal Example

text = "Violet-Indigo-Blue-Green-Yellow-Orange-Red"

# Method 1

print(text.split("-"))

# Method 2

import re

print(re.split('-', text))

# Method 3

print(list(filter(None, text.split('-'))))

# Method 4

print([x for x in re.findall(r'[^-]*|(?!-).*$', text) if x != '']) # OUTPUT: ['Violet', 'Indigo', 'Blue', 'Green', 'Yellow', 'Orange', 'Red']

Problem Formulation

Problem: Given a string, how will you split the string into a list of words using the hyphen as a delimiter?

Example

Let’s understand the problem with the help of an example.

# Input:

text = "Violet-Indigo-Blue-Green-Yellow-Orange-Red"

# Output:

['Violet', 'Indigo', 'Blue', 'Green', 'Yellow', 'Orange', 'Red']

Now without any further ado, let’s dive into the numerous ways of solving this problem.

Method 1: Using split()

Python’s built-in split() function splits the string at a given separator and returns a split list of substrings. Here’s how the split() function works: 'finxterx42'.split('x') will split the string with the character ‘x’ as the delimiter and return the following list as an output: ['fin', 'ter', '42'].

Approach: To split a string by hyphen, you can simply pass the underscore as a separator to the split('-') function.

Code:

text = "Violet-Indigo-Blue-Green-Yellow-Orange-Red"

print(text.split("-")) # ['Violet', 'Indigo', 'Blue', 'Green', 'Yellow', 'Orange', 'Red']

Related Read: Python String split()

Method 2: Using re.split()

Another way of separating a string by using the underscore as a separator is to use the re.split() method from the regex library. The re.split(pattern, string) method matches all occurrences of the pattern in the string and divides the string along the matches resulting in a list of strings between the matches. For example, re.split('a', 'bbabbbab') results in the list of strings ['bb', 'bbb', 'b'].

Approach: You can use the re.split() method as re.split('-', text) where '-' returns a match whenever the string contains a hyphen. Whenever any hyphen is encountered, the text gets separated and the split substring gets stored as an element within the resultant list.

Code:

import re

text = "Violet-Indigo-Blue-Green-Yellow-Orange-Red"

print(re.split('-', text)) # ['Violet', 'Indigo', 'Blue', 'Green', 'Yellow', 'Orange', 'Red']

Related Read: Python Regex Split

Method 3: Using filter()

Note: This approach is efficient when the resultant list contains empty strings along with substrings.

Python’s built-in filter() function filters out the elements that pass a filtering condition. It takes two arguments: function and iterable. The function assigns a Boolean value to each element in the iterable to check whether the element will pass the filter or not. It returns an iterator with the elements that passes the filtering condition.

Approach: Use the filter() method to split the string by hyphen. The function takes None as the first argument and the list of split strings as the second argument. The filter() function then iterates through the list and removes any empty elements. As the filter() method returns an object, we need to use the list() to convert the object into a list.

Code:

text = "Violet-Indigo-Blue-Green-Yellow-Orange-Red" print(list(filter(None, text.split('-')))) # ['Violet', 'Indigo', 'Blue', 'Green', 'Yellow', 'Orange', 'Red']

Related Read: Python filter()

Method 4: Using re.findall()

The re.findall(pattern, string) method scans the string from left to right, searching for all non-overlapping matches of the pattern. It returns a list of strings in the matching order- when scanning the string from left to right.

Approach: You can use the re.findall() method from the regex module to split the string by hyphen. Use ‘[^-]|(?!-).$‘ as the pattern that can be fed into the findall function to solve the problem. It simply, means a set all characters that are joined by a hyphen will be grouped together.

Code:

import re

text = "Violet-Indigo-Blue-Green-Yellow-Orange-Red" print([x for x in re.findall(r'[^_]*', text) if x != '']) # ['Python', 'Pycharm', 'Java', 'Eclipse', 'Golang', 'VisualStudio']

Related Read: Python re.findall() – Everything You Need to Know

Python | Split String by Dot

Now that we have gone through numerous ways of solving the given problem, here’s a similar programming challenge for you to solve.

Challenge: You are given a string that contains dots in it. How will you split the string using a dot as a delimiter? Consider the code below and try to split the string by dot.

# Input:

text = "stars.moon.sun.sky" # Expected Output:

['stars', 'moon', 'sun', 'sky']

Try to solve the problem yourself before looking into the given solutions.

Solution: Here are the different methods to split a string by using the dot as a delimiter/separator:

text = "a*b*c"

# Method 1

print(text.split("*")) # Method 2

print(list(filter(None, text.split('*')))) # Method 3

import re

print([x for x in re.findall(r'[^/*]*|(?!/*).*$', text) if x != '']) # Method 4

print(re.split('[/*]', text))

Conclusion

Hurrah! We have successfully solved the given problem using as many as four different ways. We then went on to solve a similar coding challenge. I hope this article helped you. Please subscribe and stay tuned for more interesting articles!

Happy coding!

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