Methods and Functions

We won't get into too much detail about methods and functions in this chapter, as we will get into more detail about them in the functions chapter.

Functions are pieces of code that can be reused, they are used to perform a specific task. Functions can take inputs, and can return outputs.

There are two types of functions, methods and functions. Methods are functions that are attached to an object, and are called using the dot notation. Functions are not attached to an object, and are called using their name.

The following example shows how to call a method:

print('Hello World!'.lower())
# > hello world!

The following example shows how to call a function:

print(len('Hello World!'))
# > 12

Built-in Functions

Python comes with a lot of built-in functions and methods with can be used to perform a wide variety of tasks. These include:

You can find a full list of built-in functions here.

print

The print function is used to print a value to the console. The following example shows how to use the print function:

print('Hello World!')
# > Hello World!

input

The input function is used to get input from the user. The following example shows how to use the input function:

name = input('Enter your name: ')
print(f'Hello {name}!')
# > Enter your name: John
# > Hello John!

type

The type function is used to get the type of a value. The following example shows how to use the type function:

print(type(1))
# > <class 'int'>
print(type(1.0))
# > <class 'float'>
print(type('Hello World!'))
# > <class 'str'>
print(type(True))
# > <class 'bool'>
print(type(None))
# > <class 'NoneType'>

int, float, str, bool

The int, float, str, and bool functions are used to convert values to integers, floats, strings, and booleans.

The following example shows how to use the int function:

print(int(1.0))
# > 1
print(int('1'))
# > 1
print(int(True))
# > 1
print(int(False))
# > 0

The following example shows how to use the float function:

print(float(1))
# > 1.0
print(float('1'))
# > 1.0
print(float(True))
# > 1.0
print(float(False))
# > 0.0

The following example shows how to use the str function:

print(str(1))
# > '1'
print(str(1.0))
# > '1.0'
print(str(True))
# > 'True'
print(str(False))
# > 'False'

The following example shows how to use the bool function:

print(bool(1))
# > True
print(bool(1.0))
# > True
print(bool('Hello World!'))
# > True
print(bool(None))
# > False

len

The len function is used to get the length of a value. The following example shows how to use the len function:

print(len('Hello World!'))
# > 12

open

The open function is used to open a file. The following example shows how to use the open function:

file = open('file.txt', 'r')
print(file.read())
# > Hello World!
file.close()

help

The help function is used to get help on a function. The following example shows how to use the help function:

help(print)
# > Help on built-in function print in module builtins:
# >
# > print(...)
# >     print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)
# >
# >     Prints the values to a stream, or to sys.stdout by default.
# >     Optional keyword arguments:
# >     file:  a file-like object (stream); defaults to the current sys.stdout.
# >     sep:   string inserted between values, default a space.
# >     end:   string appended after the last value, default a newline.
# >     flush: whether to forcibly flush the stream.

eval

The eval function is used to evaluate a string as a Python expression. The following example shows how to use the eval function:

print(eval('1 + 1'))
# > 2

Note: The eval function is dangerous, and should not be used unless you know what you are doing.

Built-in Methods

str

The str has a multitude of methods, some of which are shown below. You can find a full list of methods on the Python documentation.

lower

The lower method is used to convert a string to lowercase. The following example shows how to use the lower method:

print('Hello World!'.lower())
# > hello world!

upper

The upper method is used to convert a string to uppercase. The following example shows how to use the upper method:

print('Hello World!'.upper())
# > HELLO WORLD!

title

The title method is used to convert a string to title case. The following example shows how to use the title method:

print('hello world!'.title())
# > Hello World!

capitalize

The capitalize method is used to capitalize the first letter of a string. The following example shows how to use the capitalize method:

print('hello world!'.capitalize())
# > Hello world!

strip

The strip method is used to remove whitespace from the beginning and end of a string. The following example shows how to use the strip method:

print('   Hello World!   '.strip())
# > Hello World!

lstrip

The lstrip method is used to remove whitespace from the beginning of a string. The following example shows how to use the lstrip method:

print('   Hello World!   '.lstrip())
# > Hello World!   

rstrip

The rstrip method is used to remove whitespace from the end of a string. The following example shows how to use the rstrip method:

print('   Hello World!   '.rstrip())
# >    Hello World!

replace

The replace method is used to replace a substring with another substring. The following example shows how to use the replace method:

print('Hello World!'.replace('World', 'Universe'))
# > Hello Universe!

split

The split method is used to split a string into a list of substrings. The following example shows how to use the split method:

print('Hello World!'.split())
# > ['Hello', 'World!']

join

The join method is used to join a list of substrings into a string. The following example shows how to use the join method:

print(' '.join(['Hello', 'World!']))
# > Hello World!

startswith

The startswith method is used to check if a string starts with a substring. The following example shows how to use the startswith method:

print('Hello World!'.startswith('Hello'))
# > True

endswith

The endswith method is used to check if a string ends with a substring. The following example shows how to use the endswith method:

print('Hello World!'.endswith('World!'))
# > True

find

The find method is used to find the index of a substring. The following example shows how to use the find method:

print('Hello World!'.find('World'))
# > 6

removeprefix

The removeprefix method is used to remove a prefix from a string. The following example shows how to use the removeprefix method:

print('Hello World!'.removeprefix('Hello '))
# > World!

removesuffix

The removesuffix method is used to remove a suffix from a string. The following example shows how to use the removesuffix method:

print('Hello World!'.removesuffix(' World!'))
# > Hello