ch02.ipynb

Kernel: Python 3

import numpy as np
np.random.seed(12345)
np.set_printoptions(precision=4, suppress=True)

import numpy as np
data = [np.random.standard_normal() for i in range(7)]
data

a = [1, 2, 3]

b = a
b

a.append(4)
b

def append_element(some_list, element):
    some_list.append(element)

data = [1, 2, 3]
append_element(data, 4)
data

a = 5
type(a)
a = "foo"
type(a)

"5" + 5

a = 4.5
b = 2
# String formatting, to be visited later
print(f"a is {type(a)}, b is {type(b)}")
a / b

a = 5
isinstance(a, int)

a = 5; b = 4.5
isinstance(a, (int, float))
isinstance(b, (int, float))

a = "foo"

getattr(a, "split")

def isiterable(obj):
    try:
        iter(obj)
        return True
    except TypeError: # not iterable
        return False

isiterable("a string")
isiterable([1, 2, 3])
isiterable(5)

5 - 7
12 + 21.5
5 <= 2

a = [1, 2, 3]
b = a
c = list(a)
a is b
a is not c

a == c

a = None
a is None

a_list = ["foo", 2, [4, 5]]
a_list[2] = (3, 4)
a_list

a_tuple = (3, 5, (4, 5))
a_tuple[1] = "four"

ival = 17239871
ival ** 6

fval = 7.243
fval2 = 6.78e-5

3 / 2

3 // 2

c = """
This is a longer string that
spans multiple lines
"""

c.count("\n")

a = "this is a string"
a[10] = "f"

b = a.replace("string", "longer string")
b

a

a = 5.6
s = str(a)
print(s)

s = "python"
list(s)
s[:3]

s = "12\\34"
print(s)

s = r"this\has\no\special\characters"
s

a = "this is the first half "
b = "and this is the second half"
a + b

template = "{0:.2f} {1:s} are worth US${2:d}"

template.format(88.46, "Argentine Pesos", 1)

amount = 10
rate = 88.46
currency = "Pesos"
result = f"{amount} {currency} is worth US${amount / rate}"

f"{amount} {currency} is worth US${amount / rate:.2f}"

val = "español"
val

val_utf8 = val.encode("utf-8")
val_utf8
type(val_utf8)

val_utf8.decode("utf-8")

val.encode("latin1")
val.encode("utf-16")
val.encode("utf-16le")

True and True
False or True

int(False)
int(True)

a = True
b = False
not a
not b

s = "3.14159"
fval = float(s)
type(fval)
int(fval)
bool(fval)
bool(0)

a = None
a is None
b = 5
b is not None

from datetime import datetime, date, time
dt = datetime(2011, 10, 29, 20, 30, 21)
dt.day
dt.minute

dt.date()
dt.time()

dt.strftime("%Y-%m-%d %H:%M")

datetime.strptime("20091031", "%Y%m%d")

dt_hour = dt.replace(minute=0, second=0)
dt_hour

dt

dt2 = datetime(2011, 11, 15, 22, 30)
delta = dt2 - dt
delta
type(delta)

dt
dt + delta

a = 5; b = 7
c = 8; d = 4
if a < b or c > d:
    print("Made it")

4 > 3 > 2 > 1

for i in range(4):
    for j in range(4):
        if j > i:
            break
        print((i, j))

range(10)
list(range(10))

list(range(0, 20, 2))
list(range(5, 0, -1))

seq = [1, 2, 3, 4]
for i in range(len(seq)):
    print(f"element {i}: {seq[i]}")

total = 0
for i in range(100_000):
    # % is the modulo operator
    if i % 3 == 0 or i % 5 == 0:
        total += i
print(total)