新手上路必學(xué)的Python函數(shù)基礎(chǔ)知識，全在這里了（多段代碼舉例）

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)

my_function(x=5,?y=6,?z=7)??my_function(y=6, x=5, z=7)

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

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

In?[168]:?a?=?None??In?[169]:?def?bind_a_variable():??.....:????????global?a??.....:????????a?=?[]??.....:????????bind_a_variable()??.....:??In?[170]:?print(a)??[]

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}??

In?[171]:?states?=?['?Alabama?',?'Georgia!',?'Georgia',?'georgia',?'FlOrIda',??.....: 'south carolina##', 'West virginia?']

import?re??def?clean_strings(strings):??????result?=?[]??????for?value?in?strings:??????????value?=?value.strip()??????????value?=?re.sub('[!#?]',?'',?value)??????????value?=?value.title()??????????result.append(value)??    return result

In?[173]:?clean_strings(states)??Out[173]:??['Alabama',??'Georgia',??'Georgia',??'Georgia',??'Florida',??'South?Carolina',??'West Virginia']

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 [175]: clean_strings(states, clean_ops)  Out[175]:  ['Alabama',  'Georgia',  'Georgia',  'Georgia',  'Florida',  'South Carolina',  'West Virginia']

In [176]: for x in map(remove_punctuation, states):  .....:        print(x)  Alabama  Georgia  Georgia  georgia  FlOrIda  south carolina  West virginia

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

In?[178]:?strings.sort(key=lambda?x:?len(set(list(x))))??In?[179]:?strings??Out[179]: ['aaaa', 'foo', 'abab', 'bar', 'card']

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)

In?[180]:?some_dict?=?{'a':?1,?'b':?2,?'c':?3}??In?[181]:?for?key?in?some_dict:??.....:????????print(key)??a???b  c??

In [182]: dict_iterator = iter(some_dict)  In [183]: dict_iterator  Out[183]: 

In [184]: list(dict_iterator)  Out[184]: ['a', 'b', 'c']

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?[186]:?gen?=?squares()??In?[187]:?gen??Out[187]:???

In?[188]:?for?x?in?gen:??.....:?print(x,?end='?')??Generating?squares?from?1?to?100??1 4 9 16 25 36 49 64 81 100  

In?[189]:?gen?=?(x?**?2?for?x?in?range(100))??In?[190]:?gen??Out[190]:  at 0x7fbbd5ab29e8>  

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

In?[191]:?sum(x?**?2?for?x?in?range(100))??Out[191]:?328350??In?[192]:?dict((i,?i?**2)?for?i?in?range(5))??Out[192]: {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}  

In?[193]:?import?itertools??In?[194]:?first_letter?=?lambda?x:?x[0]??In?[195]:?names?=?['Alan',?'Adam',?'Wes',?'Will',?'Albert',?'Steven']??In?[196]:?for?letter,?names?in?itertools.groupby(names,?first_letter):??.....:????????print(letter,?list(names))?#?names是一個生成器??A?['Alan',?'Adam']??W?['Wes',?'Will']??A?['Albert']??S ['Steven']  

In [197]: float('1.2345')  Out[197]: 1.2345  In [198]: float('something')  ---------------------------------------------------------------------------  ValueError Traceback (most recent call last)  input-198-439904410854> in <module>()  ----> 1 float('something')  ValueError: could not convert string to float: 'something' 

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

In?[200]:?attempt_float('1.2345')??Out[200]:?1.2345??In?[201]:?attempt_float('something')??Out[201]: 'something  

In [202]: float((1, 2))  ---------------------------------------------------------------------------  TypeError Traceback (most recent call last)  input-202-842079ebb635> in <module>()  ----> 1 float((1, 2))  TypeError: float() argument must be a string or a number, not 'tuple'  

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

In?[204]:?attempt_float((1,?2))??---------------------------------------------------------------------------??TypeError?Traceback?(most?recent?call?last)??input-204-9bdfd730cead>?in?<module>()??----> 1 attempt_float((1, 2))  input-203-3e06b8379b6b>?in?attempt_float(x)??1?def?attempt_float(x):??2?try:??---->?3?return?float(x)??4?except?ValueError:??5?return?x??TypeError: float() argument must be a string or a number, not 'tuple'  

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()  

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: