一、isdigit()函数
isdigit()函数是检测输入字符串是否只由数字组成。如果字符串只包含数字则返回 True 否则返回 False。
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dream = "123456"
print (dream.isdigit())
# 返回:True
dream = "123abc456"
print (dream.isdigit())
# 返回:False
dream = 'abcd'
print (dream.isdigit())
# 返回:False
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二、filter() 函数
说明:filter() 函数用于过滤序列,过滤掉不符合条件的元素,返回一个迭代器对象;
如果要转换为列表,可以使用 list() 来转换。
该接收两个参数,第一个为函数,第二个为序列,序列的每个元素作为参数传递给函数进行判断,然后返回 True 或 False,最后将返回 True 的元素放到新列表中。
语法:
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filter (function, iterable)
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1、过滤出列表中的所有奇数:
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def is_odd(n):
return n % 2 = = 1
tmplist = filter (is_odd, [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ])
newlist = list (tmplist)
print (newlist)
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2、过滤出列表中的所有偶数:
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l = [x for x in range ( 10 )]
print ( list ( filter ( lambda x : x % 2 = = 0 , l)))
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3、过滤出1~100中平方根是整数的数:
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import math
def is_sqr(x):
return math.sqrt(x) % 1 = = 0
tmplist = filter (is_sqr, range ( 1 , 101 ))
newlist = list (tmplist)
print (newlist)
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4、删除1-100中素数
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L = range ( 1 , 101 )
def isprimer(n):
flag = 1
for i in range ( 2 , n):
if n % i = = 0 :
flag = 0
if flag = = 0 :
return n
print ( list ( filter (isprimer, L)))
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5、去除空格和空值
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def not_empty(s):
return s and s.strip()
filter (not_empty, [ 'A' , ' ', ' B ', None, ' C ', ' '])
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6、高阶运用
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def _odd_iter():
n = 1
while True :
n = n + 2
yield n
def _not_divisible(n):
return lambda x : x % n> 0
def primes():
yield 2
it = _odd_iter()
ftr = filter (_not_divisible( 2 ), it) #1
while True :
n = next (ftr ) #2
yield n
ftr = filter (_not_divisible(n), ftr ) #3
for n in primes():
if n < 100 :
print ( 'now:' ,n)
else :
break
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三、提取一段字符串中的数字
列表转字符串
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number = [ '12' , '333' , '4' ]
number_ = "".join(number) # 列表转字符串
print (number_) # 123334
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a = "".join( list ( filter ( str .isdigit, '123ab45' )))
print (a)
# 返回12345
b = list ( filter ( str .isdigit, '123ab45' ))
print (b)
# 返回['1', '2', '3', '4', '5']
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time_ = "2019年09月04日 11:00"
time_filter = filter ( str .isdigit, time_)
print (time_filter) # <filter object at 0x0000019358731BE0>
print ( type (time_filter)) # <class 'filter'>
time_list = list (time_filter) # ['2', '0', '1', '9', '0', '9', '0', '4', '1', '1', '0', '0']
time_str = "".join(time_list) # 转为str 201909041100
time_int = int (time_str) # 转为int 201909041100
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利用正则表达式
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import re
str_ = "12今天333天气4不错"
number = re.findall( "\d+" ,str_) # 输出结果为列表
print (number)
# 输出结果:['12', '333', '4']
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四、匹配指定字符串开头的数字
例如下面的string:
tensorflow:Final best valid 0 loss=0.20478513836860657 norm_loss=0.767241849151384 roc=0.8262403011322021 pr=0.39401692152023315 calibration=0.9863265752792358 rate=0.0
提取 calibration=0.9863265752792358 .
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# 匹配“calibration=”后面的数字
pattern = re. compile (r '(?<=calibration=)\d+\.?\d*' )
pattern.findall(string)
# ['0.9863265752792358']
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五、匹配时间,17:35:24
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string = "WARNING:tensorflow: 20181011 15:28:39 Initialize training"
pattern = re. compile (r '\d{2}:\d{2}:\d{2}' )
pattern.findall(string)
# ['15:28:39']
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提取两个下划线中的数字 比如 _500_
string
=
"WARNING:tensorflow: _500_ Initialize training"
pattern
=
re.
compile
(r
'_(\d+)_'
)
pattern.findall(string)
# 500
六、匹配时间,20181011 15:28:39
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string = "WARNING:tensorflow: 20181011 15:28:39 Initialize training"
pattern = re. compile (r '\d{4}\d{2}\d{2}\s\d{2}:\d{2}:\d{2}' )
pattern.findall(string)
# ['20181011 15:28:39']
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标签:字符,提取,string,python,pattern,list,filter,time,print From: https://www.cnblogs.com/oceaning/p/17300773.html