s = "Hello, world!"
for c in s:
print(c)
H e l l o , w o r l d !
a = [1, 2, 3, True, [5,6,7], 3.1415]
for item in a:
print("hello")
print(item)
hello 1 hello 2 hello 3 hello True hello [5, 6, 7] hello 3.1415
for i in range(10):
print(i)
0 1 2 3 4 5 6 7 8 9
range(10)
range(0, 10)
list(range(10))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
n = int(input())
15
n
15
for i in range(n, 0, -1):
print(i, i**2)
15 225 14 196 13 169 12 144 11 121 10 100 9 81 8 64 7 49 6 36 5 25 4 16 3 9 2 4 1 1
i = 15
while i > 0:
print(i, i ** 2)
i -= 1 # i = i - 1
15 225 14 196 13 169 12 144 11 121 10 100 9 81 8 64 7 49 6 36 5 25 4 16 3 9 2 4 1 1
i = 0
while True:
print(i)
i += 1
if i > 15:
break
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
i = 0
while i < 15:
i += 1
if i % 3 == 0:
continue
print(i)
1 2 4 5 7 8 10 11 13 14
if i < 15:
print("<")
elif i == 15:
print("=")
elif i == 16:
print("approximately ==")
else:
print(">")
=
if i < 15:
print("<")
else:
if i == 15:
print("=")
else:
if i == 16:
print("==")
else:
print(">")
=
for i in range(3):
print(i)
else:
print("else")
0 1 2 else
for i in range(3):
print(i)
if i == 2:
break
else:
print("else")
0 1 2
if i > 0 and i < 15:
print("OK")
OK
A = i > 0
A
True
B = i < 15
C = i == 10
if A and B:
print(1)
elif A and C:
print(2)
1
if A:
if B:
print(1)
elif C:
print(2)
1
if A and not B or not A and B:
print(1)
if i > 0 and i <= 15:
print("OK")
OK
if 0 < i <= 15:
print("OK")
OK
if i != 10:
print("Not equal!")
Not equal!
if i <> 10:
print("Not equal at all!")
File "<ipython-input-44-3d86590b689c>", line 1 if i <> 10: ^ SyntaxError: invalid syntax
a = [1, 2, 3, True, None, [5,6,7], 3.14]
a.append(17)
a
[1, 2, 3, True, None, [5, 6, 7], 3.14, 17]
a.pop()
17
a
[1, 2, 3, True, None, [5, 6, 7], 3.14]
a += ["a", "b", "c"]
a
[1, 2, 3, True, None, [5, 6, 7], 3.14, 'a', 'b', 'c']
[0] * 10
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
a = [[1,2,3]] * 5
a
[[1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3]]
a[0][0] = 0
a
[[0, 2, 3], [0, 2, 3], [0, 2, 3], [0, 2, 3], [0, 2, 3]]
a[-1][0] = 1
a
[[1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3]]
b = (1, 2, 3)
a = [1, 2, 3]
type(a)
list
type(b)
tuple
len(b)
3
b[1]
2
d = {"Monday": 1, "Tuesday": 2, "Wednesday": 3}
d["Tuesday"]
2
print(d)
{'Tuesday': 2, 'Monday': 1, 'Wednesday': 3}
d2 = {(8, 9, 2015): 80, (4, 9, 2015): 90}
d2[(4, 9, 2015)]
90
d2[123123]
--------------------------------------------------------------------------- KeyError Traceback (most recent call last) <ipython-input-71-d244718ac473> in <module>() ----> 1 d2[123123] KeyError: 123123
d[(1,2,3)] = False
d
{(1, 2, 3): False, 'Tuesday': 2, 'Monday': 1, 'Wednesday': 3}
del d[(1,2,3)]
d
{'Monday': 1, 'Tuesday': 2, 'Wednesday': 3}
for key in d:
print(key, d[key])
Tuesday 2 Monday 1 Wednesday 3
for key in sorted(d.keys()):
print(key, d[key])
Monday 1 Tuesday 2 Wednesday 3
d["Thursday"] = 4
d["Friday"] = 5
d["Saturday"] = 6
d["Sunday"] = 0
for key in sorted(d.keys()):
print(key, d[key])
Friday 5 Monday 1 Saturday 6 Sunday 0 Thursday 4 Tuesday 2 Wednesday 3
pairs = list(d.items())
pairs
[('Friday', 5), ('Tuesday', 2), ('Thursday', 4), ('Saturday', 6), ('Sunday', 0), ('Monday', 1), ('Wednesday', 3)]
pairs = [(d[key], key) for key in d]
pairs
[(5, 'Friday'), (2, 'Tuesday'), (4, 'Thursday'), (6, 'Saturday'), (0, 'Sunday'), (1, 'Monday'), (3, 'Wednesday')]
pairs.sort()
pairs
[(0, 'Sunday'), (1, 'Monday'), (2, 'Tuesday'), (3, 'Wednesday'), (4, 'Thursday'), (5, 'Friday'), (6, 'Saturday')]
d_rev = dict(pairs)
d_rev
{0: 'Sunday', 1: 'Monday', 2: 'Tuesday', 3: 'Wednesday', 4: 'Thursday', 5: 'Friday', 6: 'Saturday'}
d_rev[5]
'Friday'
dict([(1, "a"), (1, "b"), (2, "c")])
{1: 'b', 2: 'c'}
s = "Elementary, my dear Watson!"
letters = {}
for c in s:
if c not in letters:
letters[c] = 1
else:
letters[c] += 1
for key in letters:
print(key, letters[key])
3 r 2 W 1 ! 1 t 2 m 2 E 1 n 2 a 3 l 1 e 3 d 1 o 1 y 2 s 1 , 1
letters = {}
for c in s:
letters[c] = letters.get(c, 0) + 1
print(letters)
{' ': 3, 'r': 2, 'W': 1, '!': 1, 't': 2, 'm': 2, 'E': 1, 'n': 2, 'a': 3, 'l': 1, 'e': 3, 'd': 1, 'o': 1, 'y': 2, 's': 1, ',': 1}
A = set([1, 2, 3])
B = set([2, 3, 4, 5])
A.union(B)
{1, 2, 3, 4, 5}
A.intersection(B)
{2, 3}
print(A in B)
False
print(3 in B)
True
len(A)
3
len(B)
4
A.difference(B)
{1}
A | B
{1, 2, 3, 4, 5}
A & B
{2, 3}
A - B
{1}
s
'Elementary, my dear Watson!'
letters = set()
for c in s:
letters.add(c)
print(letters)
{'t', 'r', 'W', '!', 'm', 'o', 'E', 'd', 'a', 'l', 'e', 'n', 'y', ' ', 's', ','}
print("".join(sorted(letters)))
!,EWadelmnorsty
ord(".")
46
letters = set(s)
print("".join(sorted(letters)))
!,EWadelmnorsty
d
{'Friday': 5, 'Monday': 1, 'Saturday': 6, 'Sunday': 0, 'Thursday': 4, 'Tuesday': 2, 'Wednesday': 3}
d["January"]
--------------------------------------------------------------------------- KeyError Traceback (most recent call last) <ipython-input-129-77a4d1f086fd> in <module>() ----> 1 d["January"] KeyError: 'January'
d.get("January", 1234)
1234
d.get("Monday", 1234)
1
s.lower()
'elementary, my dear watson!'
print(d.get("January"))
None
if "Monday" in d:
print(d["Monday"])
else:
print(1234)
1