高阶函数
# 高阶函数
def f(x):
return x * x
# map()函数接收两个参数，一个是函数，一个是Iterable，map将传入的函数依次作用到序列的每个元素，并把结果作为新的Iterator返回。
# map()传入的第一个参数是f，即函数对象本身。由于结果r是一个Iterator，Iterator是惰性序列，因此通过list()函数让它把整个序列都计算出来并返回一个list。
r_lazy = map(f, [1, 2, 3]) # 惰性序列
r = list(r_lazy)
from functools import reduce
def add(x, y):
return x + y
r_reduce = reduce(add, [1, 4, 9])
def is_odd(n):
return n % 2 == 1
# 和map()类似，filter()也接收一个函数和一个序列。和map()不同的是，filter()把传入的函数依次作用于每个元素，然后根据返回值是True还是False决定保留还是丢弃该元素。
r_lazy_1 = filter(is_odd, [1, 2, 3, 4])
r_1 = list(r_lazy_1)
偏函数
import functools
int2 = functools.partial(int, base=2)
def f(x, d=3):
return x ** d
f4 = functools.partial(f, d=4)
f2 = functools.partial(f, d=2)
L = [('Bob', 75), ('Adam', 92), ('Bart', 66), ('Lisa', 88)]
def by_name(t):
return t[1]
sorted(L, key=by_name)
L = [3, -5, 6, -89]
sorted(L, key=abs)
L = ['bob', 'about', 'Zoo', 'Credit']
sorted(L) # ['Credit', 'Zoo', 'about', 'bob']
sorted(L, key=str.lower) # ['about', 'bob', 'Credit', 'Zoo']
sorted - 廖雪峰的官方网站 https://www.liaoxuefeng.com/wiki/1016959663602400/1017408670135712
默认情况下，对字符串排序，是按照ASCII的大小比较的，由于'Z' < 'a'，结果，大写字母Z会排在小写字母a的前面。
"""Filename globbing utility."""
import os
import re
import fnmatch
import sys
__all__ = ["glob", "iglob", "escape"]
def glob(pathname, *, recursive=False):
"""Return a list of paths matching a pathname pattern.
The pattern may contain simple shell-style wildcards a la
fnmatch. However, unlike fnmatch, filenames starting with a
dot are special cases that are not matched by '*' and '?'
patterns.
If recursive is true, the pattern '**' will match any files and
zero or more directories and subdirectories.
"""
return list(iglob(pathname, recursive=recursive))
def iglob(pathname, *, recursive=False):
"""Return an iterator which yields the paths matching a pathname pattern.
The pattern may contain simple shell-style wildcards a la
fnmatch. However, unlike fnmatch, filenames starting with a
dot are special cases that are not matched by '*' and '?'
patterns.
If recursive is true, the pattern '**' will match any files and
zero or more directories and subdirectories.
"""
it = _iglob(pathname, recursive, False)
if recursive and _isrecursive(pathname):
s = next(it) # skip empty string
assert not s
return it
def _iglob(pathname, recursive, dironly):
sys.audit("glob.glob", pathname, recursive)
dirname, basename = os.path.split(pathname)
if not has_magic(pathname):
assert not dironly
if basename:
if os.path.lexists(pathname):
yield pathname
else:
# Patterns ending with a slash should match only directories
if os.path.isdir(dirname):
yield pathname
return
if not dirname:
if recursive and _isrecursive(basename):
yield from _glob2(dirname, basename, dironly)
else:
yield from _glob1(dirname, basename, dironly)
return
# `os.path.split()` returns the argument itself as a dirname if it is a
# drive or UNC path. Prevent an infinite recursion if a drive or UNC path
# contains magic characters (i.e. r'\?C:').
if dirname != pathname and has_magic(dirname):
dirs = _iglob(dirname, recursive, True)
else:
dirs = [dirname]
if has_magic(basename):
if recursive and _isrecursive(basename):
glob_in_dir = _glob2
else:
glob_in_dir = _glob1
else:
glob_in_dir = _glob0
for dirname in dirs:
for name in glob_in_dir(dirname, basename, dironly):
yield os.path.join(dirname, name)
# These 2 helper functions non-recursively glob inside a literal directory.
# They return a list of basenames. _glob1 accepts a pattern while _glob0
# takes a literal basename (so it only has to check for its existence).
def _glob1(dirname, pattern, dironly):
names = list(_iterdir(dirname, dironly))
if not _ishidden(pattern):
names = (x for x in names if not _ishidden(x))
return fnmatch.filter(names, pattern)
def _glob0(dirname, basename, dironly):
if not basename:
# `os.path.split()` returns an empty basename for paths ending with a
# directory separator. 'q*x/' should match only directories.
if os.path.isdir(dirname):
return [basename]
else:
if os.path.lexists(os.path.join(dirname, basename)):
return [basename]
return []
# Following functions are not public but can be used by third-party code.
def glob0(dirname, pattern):
return _glob0(dirname, pattern, False)
def glob1(dirname, pattern):
return _glob1(dirname, pattern, False)
# This helper function recursively yields relative pathnames inside a literal
# directory.
def _glob2(dirname, pattern, dironly):
assert _isrecursive(pattern)
yield pattern[:0]
yield from _rlistdir(dirname, dironly)
# If dironly is false, yields all file names inside a directory.
# If dironly is true, yields only directory names.
def _iterdir(dirname, dironly):
if not dirname:
if isinstance(dirname, bytes):
dirname = bytes(os.curdir, 'ASCII')
else:
dirname = os.curdir
try:
with os.scandir(dirname) as it:
for entry in it:
try:
if not dironly or entry.is_dir():
yield entry.name
except OSError:
pass
except OSError:
return
# Recursively yields relative pathnames inside a literal directory.
def _rlistdir(dirname, dironly):
names = list(_iterdir(dirname, dironly))
for x in names:
if not _ishidden(x):
yield x
path = os.path.join(dirname, x) if dirname else x
for y in _rlistdir(path, dironly):
yield os.path.join(x, y)
magic_check = re.compile('([*?[])')
magic_check_bytes = re.compile(b'([*?[])')
def has_magic(s):
if isinstance(s, bytes):
match = magic_check_bytes.search(s)
else:
match = magic_check.search(s)
return match is not None
def _ishidden(path):
return path[0] in ('.', b'.'[0])
def _isrecursive(pattern):
if isinstance(pattern, bytes):
return pattern == b'**'
else:
return pattern == '**'
def escape(pathname):
"""Escape all special characters.
"""
# Escaping is done by wrapping any of "*?[" between square brackets.
# Metacharacters do not work in the drive part and shouldn't be escaped.
drive, pathname = os.path.splitdrive(pathname)
if isinstance(pathname, bytes):
pathname = magic_check_bytes.sub(br'[1]', pathname)
else:
pathname = magic_check.sub(r'[1]', pathname)
return drive + pathname
py381Libglob.py
"""Filename globbing utility."""
import os
import re
import fnmatch
import sys
__all__ = ["glob", "iglob", "escape"]
def glob(pathname, *, recursive=False):
"""Return a list of paths matching a pathname pattern.
The pattern may contain simple shell-style wildcards a la
fnmatch. However, unlike fnmatch, filenames starting with a
dot are special cases that are not matched by '*' and '?'
patterns.
If recursive is true, the pattern '**' will match any files and
zero or more directories and subdirectories.
"""
return list(iglob(pathname, recursive=recursive))
def iglob(pathname, *, recursive=False):
"""Return an iterator which yields the paths matching a pathname pattern.
The pattern may contain simple shell-style wildcards a la
fnmatch. However, unlike fnmatch, filenames starting with a
dot are special cases that are not matched by '*' and '?'
patterns.
If recursive is true, the pattern '**' will match any files and
zero or more directories and subdirectories.
"""
it = _iglob(pathname, recursive, False)
if recursive and _isrecursive(pathname):
s = next(it) # skip empty string
assert not s
return it
def _iglob(pathname, recursive, dironly):
sys.audit("glob.glob", pathname, recursive)
dirname, basename = os.path.split(pathname)
if not has_magic(pathname):
assert not dironly
if basename:
if os.path.lexists(pathname):
yield pathname
else:
# Patterns ending with a slash should match only directories
if os.path.isdir(dirname):
yield pathname
return
if not dirname:
if recursive and _isrecursive(basename):
yield from _glob2(dirname, basename, dironly)
else:
yield from _glob1(dirname, basename, dironly)
return
# `os.path.split()` returns the argument itself as a dirname if it is a
# drive or UNC path. Prevent an infinite recursion if a drive or UNC path
# contains magic characters (i.e. r'\?C:').
if dirname != pathname and has_magic(dirname):
dirs = _iglob(dirname, recursive, True)
else:
dirs = [dirname]
if has_magic(basename):
if recursive and _isrecursive(basename):
glob_in_dir = _glob2
else:
glob_in_dir = _glob1
else:
glob_in_dir = _glob0
for dirname in dirs:
for name in glob_in_dir(dirname, basename, dironly):
yield os.path.join(dirname, name)
# These 2 helper functions non-recursively glob inside a literal directory.
# They return a list of basenames. _glob1 accepts a pattern while _glob0
# takes a literal basename (so it only has to check for its existence).
def _glob1(dirname, pattern, dironly):
names = list(_iterdir(dirname, dironly))
if not _ishidden(pattern):
names = (x for x in names if not _ishidden(x))
return fnmatch.filter(names, pattern)
def _glob0(dirname, basename, dironly):
if not basename:
# `os.path.split()` returns an empty basename for paths ending with a
# directory separator. 'q*x/' should match only directories.
if os.path.isdir(dirname):
return [basename]
else:
if os.path.lexists(os.path.join(dirname, basename)):
return [basename]
return []
# Following functions are not public but can be used by third-party code.
def glob0(dirname, pattern):
return _glob0(dirname, pattern, False)
def glob1(dirname, pattern):
return _glob1(dirname, pattern, False)
# This helper function recursively yields relative pathnames inside a literal
# directory.
def _glob2(dirname, pattern, dironly):
assert _isrecursive(pattern)
yield pattern[:0]
yield from _rlistdir(dirname, dironly)
# If dironly is false, yields all file names inside a directory.
# If dironly is true, yields only directory names.
def _iterdir(dirname, dironly):
if not dirname:
if isinstance(dirname, bytes):
dirname = bytes(os.curdir, 'ASCII')
else:
dirname = os.curdir
try:
with os.scandir(dirname) as it:
for entry in it:
try:
if not dironly or entry.is_dir():
yield entry.name
except OSError:
pass
except OSError:
return
# Recursively yields relative pathnames inside a literal directory.
def _rlistdir(dirname, dironly):
names = list(_iterdir(dirname, dironly))
for x in names:
if not _ishidden(x):
yield x
path = os.path.join(dirname, x) if dirname else x
for y in _rlistdir(path, dironly):
yield os.path.join(x, y)
magic_check = re.compile('([*?[])')
magic_check_bytes = re.compile(b'([*?[])')
def has_magic(s):
if isinstance(s, bytes):
match = magic_check_bytes.search(s)
else:
match = magic_check.search(s)
return match is not None
def _ishidden(path):
return path[0] in ('.', b'.'[0])
def _isrecursive(pattern):
if isinstance(pattern, bytes):
return pattern == b'**'
else:
return pattern == '**'
def escape(pathname):
"""Escape all special characters.
"""
# Escaping is done by wrapping any of "*?[" between square brackets.
# Metacharacters do not work in the drive part and shouldn't be escaped.
drive, pathname = os.path.splitdrive(pathname)
if isinstance(pathname, bytes):
pathname = magic_check_bytes.sub(br'[1]', pathname)
else:
pathname = magic_check.sub(r'[1]', pathname)
return drive + pathname