Data Structures and Sequences

### 元组

In [1]:

 
tup = 4, 5, 6
tup

Out[1]:

(4, 5, 6)

In [2]:

 
nested_tup = (4, 5, 6), (7, 8)
nested_tup

Out[2]:

((4, 5, 6), (7, 8))

In [5]:

 
tuple([4, 0, 2])
​

Out[5]:

(4, 0, 2)

In [66]:

 
tup = tuple('string')
tup

Out[66]:

('s', 't', 'r', 'i', 'n', 'g')

 
Init signature: tuple(self, /, *args, **kwargs)
Docstring:    
tuple() -> empty tuple
tuple(iterable) -> tuple initialized from iterable's items
​
If the argument is a tuple, the return value is the same object.
Type:           type

In [7]:

tup[0]

Out[7]:

's'

In [8]:

 
tup = tuple(['foo', [1, 2], True])
tup[2] = False

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-8-11b694945ab9> in <module>()
      1 tup = tuple(['foo', [1, 2], True])
----> 2 tup[2] = False

TypeError: 'tuple' object does not support item assignment

In [39]:

 
tup[1].append(3)
tup

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-39-8df41c71d9f3> in <module>()
----> 1 tup[1].append(3)
      2 tup

AttributeError: 'str' object has no attribute 'append'

In [10]:

 
(4, None, 'foo') + (6, 0) + ('bar',)

Out[10]:

(4, None, 'foo', 6, 0, 'bar')

In [11]:

 
('foo', 'bar') * 4

Out[11]:

('foo', 'bar', 'foo', 'bar', 'foo', 'bar', 'foo', 'bar')

Unpacking tuples

In [12]:

 
tup = (4, 5, 6)
a, b, c = tup
b

Out[12]:

In [13]:

 
tup = 4, 5, (6, 7)
a, b, (c, d) = tup
d

Out[13]:

tmp = a a = b b = tmp

In [16]:

 
a, b = 1, 2
a
​

Out[16]:

In [17]:

Out[17]:

In [18]:

 
b, a = a, b
a
​

Out[18]:

In [19]:

Out[19]:

In [ ]:

In [20]:

 
seq = [(1, 2, 3), (4, 5, 6), (7, 8, 9)]
for a, b, c in seq:
    print('a={0}, b={1}, c={2}'.format(a, b, c))

a=1, b=2, c=3
a=4, b=5, c=6
a=7, b=8, c=9

In [24]:

 
values = 1, 2, 3, 4, 5
a, b, *rest = values
a, b
​

Out[24]:

(1, 2)

In [23]:

rest

Out[23]:

[3, 4, 5]

In [25]:

 
a, b, *_ = values

Tuple methods

In [26]:

 
a = (1, 2, 2, 2, 3, 4, 2)
a.count(2)

Out[26]:

List

In [27]:

 
a_list = [2, 3, 7, None]
tup = ('foo', 'bar', 'baz')
b_list = list(tup)
b_list
b_list[1] = 'peekaboo'
b_list

Out[27]:

['foo', 'peekaboo', 'baz']

In [28]:

 
gen = range(10)
gen
list(gen)

Out[28]:

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Adding and removing elements

In [40]:

 
b_list.append('dwarf')
b_list

Out[40]:

['red', 'baz', 'dwarf', 'foo', 'dwarf']

 
Docstring: L.append(object) -> None -- append object to end
Type:      builtin_function_or_method

In [41]:

 
b_list.insert(1, 'red')
b_list

Out[41]:

['red', 'red', 'baz', 'dwarf', 'foo', 'dwarf']

 
Docstring: L.insert(index, object) -- insert object before index
Type:      builtin_function_or_method

In [42]:

 
b_list.pop(2)
b_list

Out[42]:

['red', 'red', 'dwarf', 'foo', 'dwarf']

 
Docstring:
L.pop([index]) -> item -- remove and return item at index (default last).
Raises IndexError if list is empty or index is out of range.
Type:      builtin_function_or_method

In [43]:

 
b_list.append('foo')
b_list
b_list.remove('foo')
b_list

Out[43]:

['red', 'red', 'dwarf', 'dwarf', 'foo']

 
Docstring:
L.remove(value) -> None -- remove first occurrence of value.
Raises ValueError if the value is not present.
Type:      builtin_function_or_method

In [33]:

 
'dwarf' in b_list

Out[33]:

True

In [34]:

 
'dwarf' not in b_list

Out[34]:

False

Concatenating and combining lists

In [35]:

 
[4, None, 'foo'] + [7, 8, (2, 3)]

Out[35]:

[4, None, 'foo', 7, 8, (2, 3)]

In [44]:

 
x = [4, None, 'foo']
x.extend([7, 8, (2, 3)])
x

Out[44]:

[4, None, 'foo', 7, 8, (2, 3)]

 
Docstring: L.extend(iterable) -> None -- extend list by appending elements from the iterable
Type:      builtin_function_or_method

everything = [] for chunk in list_of_lists: everything.extend(chunk)

everything = [] for chunk in list_of_lists: everything = everything + chunk

Sorting

In [45]:

 
a = [7, 2, 5, 1, 3]
a.sort()
a

Out[45]:

[1, 2, 3, 5, 7]

 
Docstring: L.sort(key=None, reverse=False) -> None -- stable sort *IN PLACE*
Type:      builtin_function_or_method

In [46]:

 
b = ['saw', 'small', 'He', 'foxes', 'six']
b.sort(key=len)
b

Out[46]:

['He', 'saw', 'six', 'small', 'foxes']

Binary search and maintaining a sorted list

In [55]:

 
import bisect ###输出一个元素在已排序的列表中的序号，而不改变列表
c = [1, 2, 2, 2, 3, 4, 7]
bisect.bisect(c, 2)
​

Out[55]:

 
Docstring: Alias for bisect_right().
Type:      builtin_function_or_method

In [52]:

 
bisect.bisect(c, 5)
​

Out[52]:

In [53]:

 
bisect.insort(c, 6)
​

In [54]:

Out[54]:

[1, 2, 2, 2, 3, 4, 6, 7]

Slicing

In [56]:

 
seq = [7, 2, 3, 7, 5, 6, 0, 1]
seq[1:5]

Out[56]:

[2, 3, 7, 5]

In [57]:

 
seq[3:4] = [6, 3]
seq

Out[57]:

[7, 2, 3, 6, 3, 5, 6, 0, 1]

In [58]:

 
seq[:5]
seq[3:]

Out[58]:

[6, 3, 5, 6, 0, 1]

In [59]:

 
seq[-4:]
seq[-6:-2]

Out[59]:

[6, 3, 5, 6]

In [60]:

seq[::2]

Out[60]:

[7, 3, 3, 6, 1]

In [61]:

 
seq[::-1]

Out[61]:

[1, 0, 6, 5, 3, 6, 3, 2, 7]

Built-in Sequence Functions

enumerate

i = 0 for value in collection:

do something with value

i += 1

for i, value in enumerate(collection):

do something with value

In [64]:

 
some_list = ['foo', 'bar', 'baz']
mapping = {}
for i, v in enumerate(some_list):
    mapping[v] = i
mapping

Out[64]:

{'bar': 1, 'baz': 2, 'foo': 0}

 
Init signature: enumerate(self, /, *args, **kwargs)
Docstring:    
enumerate(iterable[, start]) -> iterator for index, value of iterable
​
Return an enumerate object.  iterable must be another object that supports
iteration.  The enumerate object yields pairs containing a count (from
start, which defaults to zero) and a value yielded by the iterable argument.
enumerate is useful for obtaining an indexed list:
    (0, seq[0]), (1, seq[1]), (2, seq[2]), ...
Type:           type

sorted

In [65]:

 
sorted([7, 1, 2, 6, 0, 3, 2])
sorted('horse race')

Out[65]:

[' ', 'a', 'c', 'e', 'e', 'h', 'o', 'r', 'r', 's']

 
Signature: sorted(iterable, /, *, key=None, reverse=False)
Docstring:
Return a new list containing all items from the iterable in ascending order.
​
A custom key function can be supplied to customize the sort order, and the
reverse flag can be set to request the result in descending order.
Type:      builtin_function_or_method

zip

In [67]:

 
seq1 = ['foo', 'bar', 'baz']
seq2 = ['one', 'two', 'three']
zipped = zip(seq1, seq2)
list(zipped)

Out[67]:

[('foo', 'one'), ('bar', 'two'), ('baz', 'three')]

In [ ]:

 
seq3 = [False, True]
list(zip(seq1, seq2, seq3))###转置大法

In [68]:

 
for i, (a, b) in enumerate(zip(seq1, seq2)):
    print('{0}: {1}, {2}'.format(i, a, b))

0: foo, one
1: bar, two
2: baz, three

In [ ]:

In [69]:

 
pitchers = [('Nolan', 'Ryan'), ('Roger', 'Clemens'),
            ('Schilling', 'Curt')]
first_names, last_names = zip(*pitchers#反向zip
first_names
last_names

Out[69]:

('Ryan', 'Clemens', 'Curt')

reversed

In [71]:

 
list(reversed(range(10)))

Out[71]:

[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]

 
Init signature: reversed(self, /, *args, **kwargs)
Docstring:    
reversed(sequence) -> reverse iterator over values of the sequence
​
Return a reverse iterator
Type:           type

dict

In [72]:

 
empty_dict = {}
d1 = {'a' : 'some value', 'b' : [1, 2, 3, 4]}
d1

Out[72]:

{'a': 'some value', 'b': [1, 2, 3, 4]}

In [74]:

 
d1[7] = 'an integer'
d1
​

Out[74]:

{7: 'an integer', 'a': 'some value', 'b': [1, 2, 3, 4]}

In [ ]:

d1['b']

In [ ]:

 
'b' in d1

In [75]:

 
d1[5] = 'some value'
d1
​

Out[75]:

{5: 'some value', 7: 'an integer', 'a': 'some value', 'b': [1, 2, 3, 4]}

In [76]:

 
d1['dummy'] = 'another value'
d1
​

Out[76]:

{5: 'some value',
 7: 'an integer',
 'a': 'some value',
 'b': [1, 2, 3, 4],
 'dummy': 'another value'}

In [77]:

 
del d1[5]
d1
​

Out[77]:

{7: 'an integer',
 'a': 'some value',
 'b': [1, 2, 3, 4],
 'dummy': 'another value'}

In [78]:

 
ret = d1.pop('dummy')
ret
​

Out[78]:

'another value'

In [79]:

d1

Out[79]:

{7: 'an integer', 'a': 'some value', 'b': [1, 2, 3, 4]}

In [83]:

 
list(d1.keys())
​

Out[83]:

['a', 'b', 7, 'c']

In [84]:

 
list(d1.values())

Out[84]:

['some value', 'foo', 'an integer', 12]

In [85]:

 
d1.update({'b' : 'foo', 'c' : 12})
d1

Out[85]:

{7: 'an integer', 'a': 'some value', 'b': 'foo', 'c': 12}

In [ ]:

Creating dicts from sequences

mapping = {} for key, value in zip(key_list, value_list): mapping[key] = value

In [86]:

 
mapping = dict(zip(range(5), reversed(range(5))))
mapping

Out[86]:

{0: 4, 1: 3, 2: 2, 3: 1, 4: 0}

Init signature: zip(self, /, args, *kwargs) Docstring:
zip(iter1 [,iter2 [...]]) --> zip object

Return a zip object whose .next() method returns a tuple where the i-th element comes from the i-th iterable argument. The .next() method continues until the shortest iterable in the argument sequence is exhausted and then it raises StopIteration. Type: type

Default values

if key in some_dict: value = some_dict[key] else: value = default_value

value = some_dict.get(key, default_value)

In [87]:

 
words = ['apple', 'bat', 'bar', 'atom', 'book']
by_letter = {}
for word in words:
    letter = word[0]
    if letter not in by_letter:
        by_letter[letter] = [word]
    else:
        by_letter[letter].append(word)
by_letter

Out[87]:

{'a': ['apple', 'atom'], 'b': ['bat', 'bar', 'book']}

for word in words: letter = word[0] by_letter.setdefault(letter, []).append(word)

from collections import defaultdict by_letter = defaultdict(list) for word in words: by_letter[word[0]].append(word)

Valid dict key types

In [90]:

 
hash('string')
hash((1, 2, (2, 3)))
​

Out[90]:

1097636502276347782

In [91]:

 
hash((1, 2, [2, 3])) # fails because lists are mutable

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-91-473c35a62c0b> in <module>()
----> 1 hash((1, 2, [2, 3])) # fails because lists are mutable

TypeError: unhashable type: 'list'

In [92]:

 
d = {}
d[tuple([1, 2, 3])] = 5#元组作为key
d

Out[92]:

{(1, 2, 3): 5}

set

In [95]:

 
set([2, 2, 2, 1, 3, 3])
{2, 2, 2, 1, 3, 3}

Out[95]:

{1, 2, 3}

In [103]:

 
a = {1, 2, 3, 4, 5}
b = {3, 4, 5, 6, 7, 8}

In [104]:

 
a.union(b)#并集
a | b

Out[104]:

{1, 2, 3, 4, 5, 6, 7, 8}

In [105]:

 
a.intersection(b)#交集
a & b

Out[105]:

{3, 4, 5}

In [106]:

 
c = a.copy()
c |= b
c
​

Out[106]:

{1, 2, 3, 4, 5, 6, 7, 8}

In [107]:

 
d = a.copy()
d &= b
d

Out[107]:

{3, 4, 5}

In [108]:

 
my_data = [1, 2, 3, 4]
my_set = {tuple(my_data)}
my_set

Out[108]:

{(1, 2, 3, 4)}

In [101]:

 
a_set = {1, 2, 3, 4, 5}
{1, 2, 3}.issubset(a_set)
a_set.issuperset({1, 2, 3})

Out[101]:

True

In [102]:

 
{1, 2, 3} == {3, 2, 1}#无排序

Out[102]:

True

### List, Set, and Dict Comprehensions

[

result = [] for val in collection: if

In [110]:

 
strings = ['a', 'as', 'bat', 'car', 'dove', 'python']
[x.upper() for x in strings if len(x) > 2]

Out[110]:

['BAT', 'CAR', 'DOVE', 'PYTHON']

dict_comp = {

set_comp = {

In [111]:

 
unique_lengths = {len(x) for x in strings}
unique_lengths

Out[111]:

{1, 2, 3, 4, 6}

In [112]:

 
set(map(len, strings))

Out[112]:

{1, 2, 3, 4, 6}

In [113]:

 
loc_mapping = {val : index for index, val in enumerate(strings)}
loc_mapping

Out[113]:

{'a': 0, 'as': 1, 'bat': 2, 'car': 3, 'dove': 4, 'python': 5}

Nested list comprehensions

In [114]:

 
all_data = [['John', 'Emily', 'Michael', 'Mary', 'Steven'],
            ['Maria', 'Juan', 'Javier', 'Natalia', 'Pilar']]

names_of_interest = [] for names in all_data: enough_es = [name for name in names if name.count('e') >= 2] names_of_interest.extend(enough_es)

In [115]:

 
result = [name for names in all_data for name in names #列表筛选
          if name.count('e') >= 2]
result

Out[115]:

['Steven']

In [116]:

 
some_tuples = [(1, 2, 3), (4, 5, 6), (7, 8, 9)]
flattened = [x for tup in some_tuples for x in tup]
flattened

Out[116]:

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

flattened = []

for tup in some_tuples: for x in tup: flattened.append(x)

In [ ]:

 
[[x for x in tup] for tup in some_tuples]

Functions

def my_function(x, y, z=1.5): if z > 1: return z * (x + y) else: return z / (x + y)

my_function(5, 6, z=0.7) my_function(3.14, 7, 3.5) my_function(10, 20)

Namespaces, Scope, and Local Functions

def func(): a = [] for i in range(5): a.append(i)

a = [] def func(): for i in range(5): a.append(i)

In [117]:

 
a = None
def bind_a_variable():
    global a
    a = []
bind_a_variable()
print(a)

[]

Returning Multiple Values

def f(): a = 5 b = 6 c = 7 return a, b, c

a, b, c = f()

return_value = f()

def f(): a = 5 b = 6 c = 7 return {'a' : a, 'b' : b, 'c' : c}

Functions Are Objects

In [118]:

 
states = ['   Alabama ', 'Georgia!', 'Georgia', 'georgia', 'FlOrIda',
          'south   carolina##', 'West virginia?']

In [119]:

 
import re #正则匹配
​
def clean_strings(strings):
    result = []
    for value in strings:
        value = value.strip()#去空格
        value = re.sub('[!#?]', '', value)#去特殊符号
        value = value.title()#首字母大写
        result.append(value)
    return result

In [120]:

clean_strings(states)

Out[120]:

['Alabama',
 'Georgia',
 'Georgia',
 'Georgia',
 'Florida',
 'South   Carolina',
 'West Virginia']

In [122]:

 
 
 
 
 

def remove_punctuation(value):
    return re.sub('[!#?]', '', value)
​
clean_ops = [str.strip, remove_punctuation, str.title]
​
def clean_strings(strings, ops):
    result = []
    for value in strings:
        for function in ops:
            value = function(value)
        result.append(value)
    return result
 

In [123]:

 
clean_strings(states, clean_ops)

Out[123]:

['Alabama',
 'Georgia',
 'Georgia',
 'Georgia',
 'Florida',
 'South   Carolina',
 'West Virginia']

In [124]:

 
for x in map(remove_punctuation, states):
    print(x)

   Alabama 
Georgia
Georgia
georgia
FlOrIda
south   carolina
West virginia

Anonymous (Lambda) Functions

def short_function(x): return x * 2

equiv_anon = lambda x: x * 2

def apply_to_list(some_list, f): return [f(x) for x in some_list]

ints = [4, 0, 1, 5, 6] apply_to_list(ints, lambda x: x * 2)

In [125]:

 
strings = ['foo', 'card', 'bar', 'aaaa', 'abab']

In [127]:

 
strings.sort(key=lambda x: len(set(list(x))))#按字符串所含不同字母个数排序
strings

Out[127]:

['aaaa', 'foo', 'abab', 'bar', 'card']

Currying: Partial Argument Application

def add_numbers(x, y): return x + y

add_five = lambda y: add_numbers(5, y)

from functools import partial add_five = partial(add_numbers, 5)

Generators

In [130]:

 
some_dict = {'a': 1, 'b': 2, 'c': 3}
for key in some_dict:
    print(key)

a
b
c

In [131]:

 
dict_iterator = iter(some_dict)
dict_iterator

Out[131]:

<dict_keyiterator at 0x2297b85bea8>

In [132]:

list(dict_iterator)

Out[132]:

['a', 'b', 'c']

In [133]:

 
def squares(n=10):
    print('Generating squares from 1 to {0}'.format(n ** 2))
    for i in range(1, n + 1):
        yield i ** 2

In [134]:

 
gen = squares()
gen

Out[134]:

<generator object squares at 0x000002297B842E08>

In [135]:

 
for x in gen:
    print(x, end=' ')

Generating squares from 1 to 100
1 4 9 16 25 36 49 64 81 100

Generator expresssions

In [136]:

 
gen = (x ** 2 for x in range(100))
gen

Out[136]:

<generator object <genexpr> at 0x000002297B85FAF0>

def makegen(): for x in range(100): yield x ** 2 gen = makegen()

In [138]:

 
sum(x ** 2 for x in range(100))
dict((i, i **2) for i in range(5))

Out[138]:

{0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

itertools module

In [140]:

 
import itertools
first_letter = lambda x: x[0]
names = ['Alan', 'Adam', 'Wes', 'Will', 'Albert', 'Steven']
for letter, names in itertools.groupby(names, first_letter):
    print(letter, list(names)) # names is a generator

A ['Alan', 'Adam']
W ['Wes', 'Will']
A ['Albert']
S ['Steven']

 
Init signature: itertools.groupby(self, /, *args, **kwargs)
Docstring:    
groupby(iterable, key=None) -> make an iterator that returns consecutive
keys and groups from the iterable.  If the key function is not specified or
is None, the element itself is used for grouping.
Type:           type

Errors and Exception Handling

In [141]:

 
float('1.2345')
float('something')

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-141-6d335c618d25> in <module>()
      1 float('1.2345')
----> 2 float('something')

ValueError: could not convert string to float: 'something'

In [172]:

 
def attempt_float(x):
    try:
        return float(x)
    except:
        return x

In [173]:

 
attempt_float('1.2345')
attempt_float('something')

Out[173]:

'something'

In [171]:

 
float((1, 2))

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-171-82f777b0e564> in <module>()
----> 1 float((1, 2))

TypeError: float() argument must be a string or a number, not 'tuple'

In [144]:

 
def attempt_float(x):
    try:
        return float(x)
    except ValueError:
        return x

In [174]:

 
attempt_float((1, 2))

Out[174]:

(1, 2)

In [145]:

 
def attempt_float(x):
    try:
        return float(x)
    except (TypeError, ValueError):
        return x

f = open(path, 'w')

try: write_to_file(f) finally: f.close()

f = open(path, 'w')

try: write_to_file(f) except: print('Failed') else: print('Succeeded') finally: f.close()

Exceptions in IPython

In [10]: %run examples/ipython_bug.py

AssertionError Traceback (most recent call last) /home/wesm/code/pydata-book/examples/ipython_bug.py in () 13 throws_an_exception() 14 ---> 15 calling_things()

/home/wesm/code/pydata-book/examples/ipython_bug.py in calling_things() 11 def calling_things(): 12 works_fine() ---> 13 throws_an_exception() 14 15 calling_things()

/home/wesm/code/pydata-book/examples/ipython_bug.py in throws_an_exception() 7 a = 5 8 b = 6 ----> 9 assert(a + b == 10) 10 11 def calling_things():

AssertionError:

Files and the Operating System

In [175]:

 
%pushd book-materials

[WinError 2] 系统找不到指定的文件。: 'book-materials'
C:\Users\qq123\Documents\GitHub\pydata-book

Out[175]:

['~\\Documents\\GitHub\\pydata-book']

In [176]:

 
path = 'examples/segismundo.txt'
f = open(path)

for line in f: pass

In [178]:

 
lines = [x.rstrip() for x in open(path)]
lines

Out[178]:

['Sue帽a el rico en su riqueza,',
 'que m谩s cuidados le ofrece;',
 '',
 'sue帽a el pobre que padece',
 'su miseria y su pobreza;',
 '',
 'sue帽a el que a medrar empieza,',
 'sue帽a el que afana y pretende,',
 'sue帽a el que agravia y ofende,',
 '',
 'y en el mundo, en conclusi贸n,',
 'todos sue帽an lo que son,',
 'aunque ninguno lo entiende.',
 '']

In [179]:

f.close()

In [180]:

 
with open(path) as f:
    lines = [x.rstrip() for x in f]

In [181]:

 
f = open(path)
f.read(10)
f2 = open(path, 'rb')  # Binary mode
f2.read(10)

Out[181]:

b'Sue\xc3\xb1a el '

In [182]:

 
f.tell()
f2.tell()

Out[182]:

In [183]:

 
import sys
sys.getdefaultencoding()#获得默认编码

Out[183]:

'utf-8'

In [184]:

 
f.seek(3)
f.read(1)

Out[184]:

'帽'

In [185]:

 
f.close()
f2.close()

In [186]:

 
with open('tmp.txt', 'w') as handle:
    handle.writelines(x for x in open(path) if len(x) > 1)
with open('tmp.txt') as f:
    lines = f.readlines()
lines

Out[186]:

['Sue帽a el rico en su riqueza,\n',
 'que m谩s cuidados le ofrece;\n',
 'sue帽a el pobre que padece\n',
 'su miseria y su pobreza;\n',
 'sue帽a el que a medrar empieza,\n',
 'sue帽a el que afana y pretende,\n',
 'sue帽a el que agravia y ofende,\n',
 'y en el mundo, en conclusi贸n,\n',
 'todos sue帽an lo que son,\n',
 'aunque ninguno lo entiende.\n']

In [187]:

 
import os
os.remove('tmp.txt')

Bytes and Unicode with Files

In [188]:

 
with open(path) as f:
    chars = f.read(10)
chars

Out[188]:

'Sue帽a el r'

In [189]:

 
with open(path, 'rb') as f:
    data = f.read(10)
data

Out[189]:

b'Sue\xc3\xb1a el '

In [192]:

 
data.decode('utf8')
​

Out[192]:

'Sueña el '

In [193]:

 
data[:4].decode('utf8')

---------------------------------------------------------------------------
UnicodeDecodeError                        Traceback (most recent call last)
<ipython-input-193-0ad9ad6a11bd> in <module>()
----> 1 data[:4].decode('utf8')

UnicodeDecodeError: 'utf-8' codec can't decode byte 0xc3 in position 3: unexpected end of data

In [195]:

 
sink_path = 'sink.txt'
with open(path) as source:
    with open(sink_path, 'xt', encoding='iso-8859-1') as sink:
        sink.write(source.read())
with open(sink_path, encoding='iso-8859-1') as f:
    print(f.read(10))

---------------------------------------------------------------------------
FileExistsError                           Traceback (most recent call last)
<ipython-input-195-83e4bc815eaa> in <module>()
      1 sink_path = 'sink.txt'
      2 with open(path) as source:
----> 3     with open(sink_path, 'xt', encoding='iso-8859-1') as sink:
      4         sink.write(source.read())
      5 with open(sink_path, encoding='iso-8859-1') as f:

FileExistsError: [Errno 17] File exists: 'sink.txt'

In [196]:

 
os.remove(sink_path)

In [197]:

 
f = open(path)
f.read(5)
f.seek(4)
f.read(1)
f.close()

In [198]:

%popd

C:\Users\qq123\Documents\GitHub\pydata-book
popd -> ~\Documents\GitHub\pydata-book

跨界混子

萌新向Python数据分析及数据挖掘第二章 pandas 第三节 Built-in Data Structures, Functions, Data Structures and Sequences

Built-in Data Structures, Functions,

Data Structures and Sequences

Unpacking tuples

Tuple methods

List

Adding and removing elements

Concatenating and combining lists

Sorting

Binary search and maintaining a sorted list

Slicing

Built-in Sequence Functions

enumerate

do something with value

do something with value

sorted

zip

reversed

dict

Creating dicts from sequences

Default values

Valid dict key types

set

Nested list comprehensions

Functions

Namespaces, Scope, and Local Functions

Returning Multiple Values

Functions Are Objects

Anonymous (Lambda) Functions

Currying: Partial Argument Application

Generators

Generator expresssions

itertools module

Errors and Exception Handling

Exceptions in IPython

In [10]: %run examples/ipython_bug.py

Files and the Operating System

Bytes and Unicode with Files

公告

跨界混子

萌新向Python数据分析及数据挖掘 第二章 pandas 第三节 Built-in Data Structures, Functions, Data Structures and Sequences

Built-in Data Structures, Functions,

Data Structures and Sequences

Unpacking tuples

Tuple methods

List

Adding and removing elements

Concatenating and combining lists

Sorting

Binary search and maintaining a sorted list

Slicing

Built-in Sequence Functions

enumerate

do something with value

do something with value

sorted

zip

reversed

dict

Creating dicts from sequences

Default values

Valid dict key types

set

Nested list comprehensions

Functions

Namespaces, Scope, and Local Functions

Returning Multiple Values

Functions Are Objects

Anonymous (Lambda) Functions

Currying: Partial Argument Application

Generators

Generator expresssions

itertools module

Errors and Exception Handling

Exceptions in IPython

In [10]: %run examples/ipython_bug.py

Files and the Operating System

Bytes and Unicode with Files

公告

萌新向Python数据分析及数据挖掘第二章 pandas 第三节 Built-in Data Structures, Functions, Data Structures and Sequences