What are representations of numbers in Python with examples.
In this lecture, we will learn about a few more representations of numbers in Python. Hexadecimal Using the function hex() you can convert numbers into a hexadecimal format:
hex(246) '0xf6' hex(512) '0x200'
Using the function bin() you can convert numbers into their binary format.
**Exponentials** The function pow() takes two arguments, equivalent to x^y. With three arguments it is equivalent to (x^y)%z, but may be more efficient for long integers. ```js pow(3,4) 81 pow(3,4,5) 1
Absolute Value The function abs() returns the absolute value of a number. The argument may be an integer or a floating point number. If the argument is a complex number, its magnitude is returned.
abs(-3.14) 3.14 abs(3) 3
Round The function round() will round a number to a given precision in decimal digits (default 0 digits). It does not convert integers to floats.
round(3,2) 3 round(395,-2) 400 round(3.1415926535,2) 3.14
Python has a built-in math library that is also useful to play around with in case you are ever in need of some mathematical operations. Explore the documentation here!
String objects have a variety of methods we can use to save time and add functionality. Let’s explore some of them in this lecture:
s = 'hello world'
Changing case We can use methods to capitalize the first word of a string, or change the case of the entire string.
# Capitalize first word in string s.capitalize() 'Hello world' s.upper() 'HELLO WORLD' s.lower() 'hello world'
Remember, strings are immutable. None of the above methods change the string in place, they only return modified copies of the original string.
s 'hello world'
To change a string requires reassignment:
s = s.upper() s 'HELLO WORLD' s = s.lower() s 'hello world'
Location and Counting
s.count('o') # returns the number of occurrences, without overlap 2 s.find('o') # returns the starting index position of the first occurence 4
Formatting The center() method allows you to place your string ‘centered’ between a provided string with a certain length. Personally, I’ve never actually used this in code as it seems pretty esoteric…
s.center(20,'z') 'zzzzhello worldzzzzz'
The expandtabs() method will expand tab notations \t into spaces:
'hello\thi'.expandtabs() 'hello hi'
is check methods These various methods below check if the string is some case. Let’s explore them:
s = 'hello'
isalnum() will return True if all characters in s are alphanumeric
isalpha() will return True if all characters in s are alphabetic
islower() will return True if all cased characters in s are lowercase and there is at least one cased character in s, False otherwise.
isspace() will return True if all characters in s are whitespace.
istitle() will return True if s is a title cased string and there is at least one character in s, i.e.
uppercase characters may only follow uncased characters and lowercase characters only cased ones. It returns False otherwise.
isupper() will return True if all cased characters in s are uppercase and there is at least one cased character in s, False otherwise.
Another method is endswith() which is essentially the same as a boolean check on s[-1]
Built-in Reg. Expressions Strings have some built-in methods that can resemble regular expression operations. We can use split() to split the string at a certain element and return a list of the results. We can use partition() to return a tuple that includes the first occurrence of the separator sandwiched between the first half and the end half.
s.split('e') ['h', 'llo'] s.partition('l') ('he', 'l', 'lo')
Great! You should now feel comfortable using the variety of methods that are built-in string objects!