リストの基本的なPython 3コード

私が以前の記事に記載したことのすべてのPython 3の例.

インタビューのリストとベクトルの必須コード

エダ族QAモルト・ 3月19日・ 7分読む

#coding #beginners #career #interview

この構文の多くにはバリエーションがありますが、1つの方法を知っている限り、あなたは元気です.私はほとんどの場合、pythonicな方法を見つけようとしました.あなたはカンニングペーパーとしてこれを使用することができます.

基礎

# Create a list
mylist = []

# Add an element to the front or back
mylist.append( "abc" )
mylist.insert( 0, "def" )

# Pop element off front or back
end = mylist.pop()
start = mylist.pop( 0 )

# Forward iterate over elements
for item in mylist:
    print( item )

# Get the length of list
len( mylist )

# Test if empty
if not mylist:
    print( "list is empty" )

ロケーションベースの操作

# Get item at location
mylist[2]

# Insert an item at location
mylist.insert( 3, "abc" ) 

# Remove an item from location
del mylist[2]

# Replace/Assign item at location
mylist[1] = "def"

ソートと検索

# Find an item
if item in mylist:
    index = mylist.index(item)

# Using `index` and error handling
try:
    index = mylist.index( 'abc' )
except ValueError:
    index = None

# Using `next` and filtering
next((x for x in mylist if x == 'ghif'), None)


# Find and remove an item
if item in mylist:
    mylist.remove( item )

# with error handling
try:
    mylist.remove( item )
except ValueError:
    pass


# Find last matching item
# Index of found item, or None
next( (index for index in reversed( range( len( mylist ) ) ) if mylist[index] == item), None)

# Alternately, reverse list and use "Find an item", but that copies the list
revlist = mylist[::-1]
if item in revlist:
    index = revlist.index( item )


# Sort by natural order
# in-place sort
mylist.sort()

# Sort with custom comparator
mylist = [ ('a', 10), ('b', 7), ('c',13), ('d',1) ]
# sort by a key (sub-element
mylist.sort( key = lambda item: item[1] )
# custom comparator
def compare_fn( a, b ):
    return some_cond( a, b )
mylist.sort( key = functools.cmp_to_key( compare_fn ) )

セグメント操作

# Split the list at arbitrary location
tail_of_list = mylist[2:]
head_of_list = mylist[:2]

# Multiple splits based on a match
mylist = ['a', 'b', 'c', 'd', 'b', 'e']
[list(y) for x, y in itertools.groupby( mylist, lambda z: z == 'b') if not x]

# Clear the list
mylist.clear()

# Remove segment
# delete from position 1 up to, but excluding position 3
del mylist[1:3]

# Concatenate lists
mylist + other_list

# Insert list at location
# list slicing replaces the segment of list with another one, here we replace a zero-length slice
mylist[1:1] = other_list

# Get a sublist
# sublist starting at position 1 up to, but excluding, position 3
mylist[1:3]

より多くの反復

# Backward
for item in reversed( mylist ):
    print( item )

# Partial segment iteration
# using itertools.islice avoids copying the list (which is what would happen if you used a slice)
for item in itertools.islice( mylist, 1, 4 ):
    print( item )

# Skipping elements
# step from element 1 to 6 (exclusive) by 2
for item in itertools.islice( mylist, 1, 6, 2 ):
    print( item )

創造

# Create from a static list of items
mylist = [ 'abc', 'def', 'ghi']

# Create a range of numbers
# a list of numbers from 10..20 (exclusive)
numbers = list( range( 10, 20 ) )

データ操作

# Mapping
[number * 10 for number in numbers]

# Filtering
[number for number in numbers if number % 2 == 0]

# Fold / Reduce
# Summing up numbers using builtin add
functools.reduce( operator.add, numbers )
# Joining string representations of items
functools.reduce( lambda left,right: str( left ) + '/' + str( right ), mylist )

# Zip
# the zip function produces a list of tuples
zip( lista, listb )
# to alternate items into one list use reduce
functools.reduce( operator.add, zip( lista, listb ) )

上級

# Swap elements at two locations
mylist[3], mylist[5] = mylist[5], mylist[3]

# Reserve capacity
# Python lists do not expose capacity

# Replace content in a list
mylist[:] = other_list

# Compare two lists
lista == listb

# Search a sorted list
# bisect_left/bisect_right work with sorted lists,
# find an item ndx using bisect_left, finds the left-most item
ndx = bisect_left( numbers, 4 )
if ndx != len(numbers) and numbers[ndx] == 4
    print( "Found at {}".format(ndx) )


# Iterators
# Manually stepping through an iterator
myiter = iter( mylist )
while True:
    try:
        n = next( myiter )
        print(n)
    except StopIteration:
        break

# Multiple iterators at the same time
itera = iter( lista )
iterb = iter( listb )
while True:
    try:
        a = next( itera )
        b = next( iterb )
        print( a, b )
    except StopIteration:
        break

あなたは偉大なプログラマになるためのより多くの方法を学びたいですか?私の本What is Programming?を読んでください.私は人々、理由ソフトウェアが存在するのを見ます、そのソフトウェアの中心のコードとあなた、キーボードの後の人.