1. How to split a string containing multiple delimiters
Actual cases:
We want to split a string into different fields based on the split symbol. The string contains a number of different delimiters, for example: s = ‘ab; cd|efg|hi,jkl|mn\topq; RST, the sale \ txyz ‘<, >, <; >, < | >, < > \ t is symbol segmentation, how to deal with?
Solution:
Method 1: Use the str.split() method continuously, processing one split symbol at a time
Method 2: Use the re.split() method of regular expressions, recommended.
s='ab; cd|efg|hi,jkl|mn\topq; rst,uvw\txyz'
s.split('|,; ')
s.split('; ')
[ss.split('|') for ss in s.split('; ')]
list(map(lambda ss:ss.split('|'),s.split('; ')))
t=[]
t.extend([1.2.3])
t.extend([4.5.6])
map(t.extend())
[ss.split('|') for ss in s.split('; ')]
sum([ss.split('|') for ss in s.split('; ')], [])def my_split(s,seps):
res=[s]
for sep in seps:
t=[]
list(map(lambda ss: t.extend(ss.split(sep)),res))
res=t
return res
my_split(s,',; |\t')
from functools import reduce
reduce(lambda l, sep:sum(map(lambda ss:ss.split(sep),1), []),',; |\t',[s]
my_splits== lambda s,seps:reduce(lambda l, sep:sum(map(lambda ss:ss.split(sep),1),[]),seps,[s]
Copy the code2. How to check whether string A begins or ends with string B
Discussion questions:
How do I determine whether string A begins or ends with string B?
Actual cases:
A file directory contains a series of files:
quicksort.c
graph.p
heap.java
install.sh
stack.cpp
Copy the codeWrite a program to add user executable permissions to all of the.sh and.py files.
Solution:
Use the str.startswith() and str.endswith() methods (note: Arguments are tuples for multiple matches)
fn='aaa.py'
fn.endswith('.py')
fn.endswith('.sh'.'.py')
import os
os.listdir('. ')
s=os.stat('b.py')
s.st_mode|0o100
oct(s.st_mode|0o100)
od.chmod('b.py',s.st_mode |0o100)
import stat
stat.S_IXUSR
for fn in os.listdir():
if fn.endswith('.py'.'.sh')
fs=os.stat(fn)
os.chmod(fn,fs.st_mode | stat.S_IXUSR)
Copy the code3. How to adjust the format of the Chinese text of a string
Discussion questions:
How to format the text of a string?
Actual cases:
The date format of the logo file is’ YYYY-MM-DD ‘. We want to change the date format to ‘mm/ DD/YYYY ‘. 2019-07-23’=>’07/23/2019’.
Solution:
Use the regular expression re.sub() method for string substitution, using the regular expression capture group, capture the content of each part, adjust the order of each capture group in the replacement string.
ls /var/log
cat/var/log/dpkg.log1.
f=open('/var/log/dpkg.log.1')
log=f.read()
import re
re.sub(p,r,s)
print(re.sub(r'(\d{4})-(\d{2})-(\d{2})'.r'\2/\3/\1',log))
print(re.sub(r'(? P
\d{4})-(? P
\d{2})-(? P
\d{2})'
.r'\g<m>/\g<y>',log))
Copy the code4. How to concatenate multiple small strings into one large string
Discussion questions:
How do I concatenate a small string into a large string?
Actual cases:
When designing the network program, we customize a udP-based network protocol to pass a series of parameters to the server in a fixed order:
hwdetect: "< 0112 >"
gxDepthBits: 32 "< >"
gxResolution: "< 1024 * 768 >"
gcRefresh: "< > 60." "" fullAlpha: "< 1 >" lodDist: "< 100 >" DistCall: "< 500 >"
Copy the codeIn the program we collect the parameters into the list in order:
[” < 0112 > < 32 “, “>”, “< 1024 >”, “< > 60”, “< 1 >, < 100.00 > < 500.00 >”, “]
Finally, we need to splice each parameter into a data for submission.
32 “< 0112 > < > < 1024 > < 60 > < 1 > < 100 > < 500 >”
Solution:
Method 1: Iterate over the list, concatenating each string in sequence using the “+” operation.
Method 2: Use str.join() to concatenate all strings in the list more quickly.
L = [" < 0112 > ""," < > 32 ", "< 1024 >", "< 60 >", "< 1 >, < 100.00 >", "< 500.00 >"] s = 'for x in l: s+=x s.join(iterable)->str timeit ''.join(l) timeit reduce(str.__add__,1)Copy the code5. How to align strings left, right, and center
Actual cases:
A dictionary stores a list of attribute values: {
"lodDist": 100.00."SmallCull": 0.04."DistCull": 500.00."trilinear": 40."farclip": 477,Copy the code} In the program, we want to output its contents in integer format, how to handle?
lodDist:100.00,
SmallCull:0.04,
DistCull:500.00,
trilinear:40,
farclip:477.Copy the codeSolution:
Str.ljust (),str.rjust(),str.center()
Method 2: Use the format method, passing arguments like ‘<20>,’>20′,’^20′ to accomplish the same task.
s='abc'
s.ljust(10)
'abc '
s.rjust(10)
' abc'
format(s,'< 10')
format(s,'> 10')
format(s,'^ 10')
format(123.'+')
format(- 123..'+')
format(- 123..'> + 10'
format(- 123..'+ 10 =')
format(- 123..'0 = + 10')
format(+546.'0 = + 10')
d={ 'lodDist':100.00.'SmallCull':0.04.'DistCull':500.00.'trilinear':40.'farclip':477,}
w=max(map(len,d.keys()))
for k,v in d.items():
print(k.ljust(w),':',v)
Copy the code6. How to string characters that are not needed
Discussion questions:
How to remove unnecessary characters from a string?
Actual cases:
1. Filter out redundant white space characters in user input.
2. Filter ‘\r’ in a Windows-edited text:
'hello world\r\n'
3. Remove Unicode combination symbols from text:
"Ni ha, ch ǐ fan '
Solution:
Method 1: strip(),lstrip(),rstrip() methods strip both ends of the string.
s=' hellowowd'
s.strip()
s.lstrip()
s.rstrip()
Copy the codeMethod 2: Delete characters in a single position by slicing and splicing.
s2='abc:1234'
s2[:3]+s2[4:]
'abc1234'
Copy the codeMethod three: The string replace() method or the regular expression re.sub() removes arbitrary strings
s3=' abc xyz '
s3.replace()
s3=' \t abc \t,xtz'
import re
re.sub('[ \t\n]'.' ',s3)
Copy the codeMethod 4: String translate(), which can delete many different characters
s='abc1234xyz'
s.translate({ord('a') :'X'})
s.maketrans('abcxyz'.'XYZABC')
s.translate(s.maketrans('abcxyz'.'XYZABC'))
s.translate({ord('a') :None})
Copy the codeCase 4:
s4='ni ha, ch ǐ fan'C = a len (c)import unicodedata
unicodedata.combining(c[1])
[ord(c) for c in s4 if unicodedata.combining(c)]
dict.formkeys([ord(c) for c in s4 if unicodedata.combining(c)],None)
s4.translate(dict.formkeys([ord(c) for c in s4 if unicodedata.combining(c)],None))
Copy the codeSplit (),replace(),translate(),format(),strip()…