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Result: The program shows that the 2 collections are separate. They occupy different locations in memory.
List: The list built-in method copied all the tuple's elements into a separate, new collection.
Python program that converts tuple to list
vegetables = ("carrot", "squash", "onion")
# Convert to list.
veg2 = list(vegetables)
veg2.append("lettuce")
# Print results.
print(vegetables)
print(veg2)
Output
('carrot', 'squash', 'onion')
['carrot', 'squash', 'onion', 'lettuce']
Tip: We pass Join() a tuple, and the result is a string containing the tuple's items.
Python program that converts tuple, string
tup = ("rabbit", "mouse", "gorilla", "giraffe")
# Join tuple with no space.
s = "".join(tup)
print(s)
# Join tuple with slash.
s = "/".join(tup)
print(s)
Output
rabbitmousegorillagiraffe
rabbit/mouse/gorilla/giraffe
Separators: We join() together the strings with no separator, and with a semicolon.
Tip: Join can handle any iterable collection, not just tuples and lists. Try it with a set.
Python program that converts list, string
vehicles = ["car", "truck", "tractor"]
# Convert list to string with join.
result = "".join(vehicles)
# Convert with semicolons separating strings.
result2 = ";".join(vehicles)
print(result)
print(result2)
Output
cartrucktractor
car;truck;tractor
And: A view is different from a list. It cannot be manipulated in the same ways.
Items: We get a view of the dictionary with items() and then convert that to a list. So we actually convert the dictionary to a list.
Tip: With dictionary views, we can change the order. For example, we can use the sorted() method to reorder elements in a view.
Python program that converts dictionary
vegetables = {"carrot": 1, "squash": 2, "onion": 4}
# Convert dictionary to list of tuples.
items = list(vegetables.items())
for item in items:
print(len(item), item)
Output
2 ('carrot', 1)
2 ('squash', 2)
2 ('onion', 4)
Int: This method receives a number and returns the integral form of that number.
So: If we pass 1.5 to int(), it will return 1. It always removes the fractional part of the number.
Python program that converts to int
floating = 1.23456
# Convert to int and print.
print(floating)
print(int(floating))
Output
1.23456
1
And: We show the value types by using them. We use len() on the string and add one to the number.
So: The string "123" has three characters. And the number 123 is increased to 124 when we add one to it.
Python program that converts int, string
# Convert number to string.
number = 123
value = str(number)
# Print the string and its character count.
print(value)
print(len(value))
# Convert string to number.
number2 = int(value)
# Print the number and add one.
print(number2)
print(number2 + 1)
Output
123
3
123
124
Note: The repr and str methods (with no underscores) are used on instances of a class. If the __repr__ method is defined, it will be used.
Tip: Classes like list also have repr (representation) methods. This is why you can directly print a list.
Python program that converts class to string
class Test:
def __init__(self):
self.size = 1
self.name = "Python"
def __repr__(self):
# Return a string.
return "Size = " + str(self.size) + ", Name = " + str(self.name)
t = Test()
# Str and repr will both call into __repr__.
s = str(t)
r = repr(t)
# Display results.
print(s)
print(r)
Output
Size = 1, Name = Python
Size = 1, Name = Python
Python program that gets list of chars
value = "cat"
# Get chars from string with list comprehension.
list = [c for c in value]
print(list)
Output
['c', 'a', 't']
Decode: To convert from the bytes data back into a string, we can use the decode method. We again must provide an encoding string.
Python program that converts bytes, string
# Convert from string to bytes.
value = "carrot"
data = bytes(value, "ascii")
print(data)
# Convert bytes into string with decode.
original = data.decode("ascii")
print(original)
Output
b'carrot'
carrot
Note: Large files have many bytes. In an interface, displaying this number is awkward and hard to read.
Convert: One megabyte contains 1024 kilobytes. And 1 kilobyte contains 1024 bytes.
So: To get from bytes to megabytes, we divide by 1024, and then by 1024 again: two divisions are needed.
And: To go from kilobytes to megabytes, we need just one division by 1024. This is simple, but testing is important.
Python program that converts bytes, megabytes
def bytestomegabytes(bytes):
return (bytes / 1024) / 1024
def kilobytestomegabytes(kilobytes):
return kilobytes / 1024
# Convert 100000 bytes to megabytes.
megabytes1 = bytestomegabytes(100000)
print(100000, "bytes =", megabytes1, "megabytes")
# 1024 kilobytes to megabytes.
megabytes2 = kilobytestomegabytes(1024)
print(1024, "kilobytes =", megabytes2, "megabytes")
Output
100000 bytes = 0.095367431640625 megabytes
1024 kilobytes = 1.0 megabytes