a = 10
a
10
type(a)
int
a = 1.0
a
1.0
type(a)
float
a = 1 / 2
a
0.5
type(a)
float
s = 'Hello world!'
s
'Hello world!'
len(s)
12
s[1]
'e'
'Foo' + 'Bar'
'FooBar'
l = [1, 2, 3]
l
[1, 2, 3]
type(l)
list
l = list(range(1, 10))
l
[1, 2, 3, 4, 5, 6, 7, 8, 9]
len(l)
9
l[-1]
9
l[:5]
[1, 2, 3, 4, 5]
l[5:]
[6, 7, 8, 9]
l[::2]
[1, 3, 5, 7, 9]
l[::-1]
[9, 8, 7, 6, 5, 4, 3, 2, 1]
l.append([10, 11, 12])
l
[1, 2, 3, 4, 5, 6, 7, 8, 9, [10, 11, 12]]
l[-1]
[10, 11, 12]
l.extend([13, 14, 15])
l
[1, 2, 3, 4, 5, 6, 7, 8, 9, [10, 11, 12], 13, 14, 15, 13, 14, 15]
l = range(100000)
d = {'a': 1, 'b':2, 'c': 3}
d
{'c': 3, 'a': 1, 'b': 2}
type(d)
dict
d['a']
1
d.keys()
dict_keys(['c', 'a', 'b'])
d.values()
dict_values([3, 1, 2])
for k, v in d.items():
print(k, v)
c 3 a 1 b 2
s = {'a', 'b', 'c', 'c'}
s
{'a', 'b', 'c'}
type(s)
set
's' in s
False
s.union({'a', 'b', 'f'})
{'a', 'b', 'c', 'f'}
def square_loop(l):
rv = []
for v in l:
rv.append(v**2)
return rv
square_loop(range(5))
[0, 1, 4, 9, 16]
def square_comprehension(l):
return [v**2 for v in l]
square_comprehension(range(5))
[0, 1, 4, 9, 16]
l = range(100000)
%timeit square_loop(l)
10 loops, best of 3: 46.3 ms per loop
%timeit square_comprehension(l)
10 loops, best of 3: 41.3 ms per loop
import math
math.pi
3.141592653589793
math.sqrt(2)
1.4142135623730951
math.exp(1)
2.718281828459045
math.log(math.e)
1.0