1.3. Python Built-In Methods#

from itertools import chain

# concatenate ranges
new_range = chain(range(5), range(5, 10))
for num in new_range:
    print(num, end=" ")

0 1 2 3 4 5 6 7 8 9 

# some consonants
consonants = ["d", "f", "k", "l", "n", "p"]
# some vowels
vowels = ["a", "e", "i", "o", "u"]
# resultatnt list
res = list(chain(consonants, vowels))

# sorting the list
res.sort()
print(res)

['a', 'd', 'e', 'f', 'i', 'k', 'l', 'n', 'o', 'p', 'u']

li = ["123", "456", "789"]

res = list(map(int, list(chain.from_iterable(li))))

sum_of_li = sum(res)

print("res =", res, end="\n\n")
print("sum =", sum_of_li)

res = [1, 2, 3, 4, 5, 6, 7, 8, 9]

sum = 45

a = {"a", "b"}
set(["a", "b"])

b = {"b", "c"}
b
set(["c", "b"])

a |= b
a

{'a', 'b', 'c'}

Working with text

In Python, you can create file objects with the built-in function open. When you call open, you need to specify the file name and how to open the file:

  • f = open (filename,method)
    • A filename is the name of a file that exists on disk. Common ways to open a file are:
  • "r"   # to read an existing file
  • “w” # create a new file and write
  • “a” # if the file exists, write to the end of the file. If the file does not exist, a new file is created and written”
    • import os

    f = open("harrypotter.txt", "w")
f.write("This is hogwarts")
f.write(" This is the chamber of secrets \n")
f.close()

    f = open("harrypotter.txt", "r")
content = f.read()
print(content)
f.close()

    This is hogwarts This is the chamber of secrets 

    f = open("Ron.txt", "w")
print(f.closed)
f.write("I love Quidditch")
f.close()
print(f.closed)

    False
True

    # delete contents of a file
open("Ron.txt", "w").close()
open("harrypotter.txt", "w").close()

    os.remove("Ron.txt")
os.remove("harrypotter.txt")

    Using context manager

    with open("readme.txt", "w") as f:
    f.write("Create a new text file!")

    # delete file
open("readme.txt", "w").close()

    with open("new.txt", "w") as f:
    f.write("Hello World!")
print(f.closed)

    True

    with open("new.txt", "r") as f:
    print(f.read())

    Hello World!

    # delete file
open("new.txt", "w").close()

    os.remove("readme.txt")
os.remove("new.txt")

    Pickle

    The first step is to grab the object’s data out of memory and convert it into an ordered text, called serialization.

    The second step is to save the text to a file.

    import pickle

    class Animal(object):
    have_trunk = True
    howtheyreproduce = "zygote"


# step 1: converting to string
winter = Animal()
pickle_string = pickle.dumps(winter)

# step 2: saving as a text
with open("winter.pkl", "wb") as f:
    f.write(pickle_string)

    # step 1: converting to string
winter = Animal()
pickle_string = pickle.dumps(winter)

# all at once
with open("winter.pkl", "wb") as f:
    pickle.dump(winter, f)

    # reading a file
with open("winter.pkl", "rb") as f:
    winter = pickle.load(f)
print(winter.have_trunk)

    True

    os.remove("winter.pkl")