Yyds dry inventory standard input of Python skills

1、 The contents of a single file can be used as standard input

create file std.py

import
sys




for
line
in
sys.
stdin:


print(
line,
end
=
"")


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stay linux Run under cat /etc/passwd | python std.py

perhaps python std.py < /etc/passwd

It will /etc/passwd Print out the contents of , Pass in the program sys.stdin obtain

sys.stdin Is a normal file object , In addition to reading from standard input , Nothing special . We can also use sys.stdin Call the method of the file object . Such as calling read The function reads everything in the standard input .

create file std2.py

import
sys




print(
sys.
stdin.
read())


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function cat /etc/passwd | python std2.py

Read the contents of multiple files as standard input

Use fileinput, You can read multiple files given in the command line arguments in turn . In most cases , We call directly fileinput Modular input Method to read the contents by line . For example, create a file read_file.py

import
fileinput




for
line
in
fileinput.
input():


print(
line,
end
=
"")


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stay linux Run under python read_stdin.py /etc/passwd /etc/passwd-, Multiple file contents can be output

because fileinput You can read the contents of multiple files , therefore fileinput Some methods are provided to let us know which file the currently read content belongs to . fileinput The common methods used in this paper are ：

1、filename： File name currently being read ;

2、fileno： The descriptor of the file ;

3、filelineno： The line being read is the line number of the current file ;

4、isfirstline： Whether the line being read is the first line of the current file ;

5、isstdin： Reading file or reading content directly from standard input .  

The code is as follows ：

import
fileinput




for
line
in
fileinput.
input():


meta
= [
fileinput.
filename(),
fileinput.
fileno(),
fileinput.
filelineno(),
fileinput.
isfirstline(),
fileinput.
isstdin()]


print(
meta)


print(
line,
end
=
"")


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