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wesm
GitHub Repository: wesm/pydata-book
Path: blob/3rd-edition/ch02.ipynb
1797 views
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 = "espaƱol" 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)