python script的context环境工具:
Current working directory
os.getcwd
Command-line arguments
sys.argv
Shell variables
os.environ
Standard streams
sys.stdin sys.stdout sys.stderr
这些工具被用来输入到脚本或者被当作配置参数。
Current working directory:
在执行脚本时，如果不包含完整的路径，则首先搜索当前目录
Standard streams
标准流有三种类型：
sys.stdin 接收键盘输入
sys.stdout 输出到屏幕
sys.stderr 输出到屏幕
for example
teststream.py
def interact():
print(‘Hello stream world‘) # print sends to sys.stdout
while True:
try:
reply = input(‘Enter a number>‘) # input reads sys.stdin
except EOFError:
break # raises an except on eof
else: # input given as a string
num = int(reply)
print("%d squared is %d" % (num, num ** 2))
print(‘Bye‘)
if __name__ == ‘__main__‘:
interact()
D:\Python33>python teststream.py Hello stream world Enter a number>12 12 squared is 144 Enter a number>100 100 squared is 10000 Enter a number>
D:\Python33>type input.txt 1 2 3 4 5 6 7 8 9 10
D:\Python33>python teststream.py < input.txt Hello stream world Enter a number>1 squared is 1 Enter a number>2 squared is 4 Enter a number>3 squared is 9 Enter a number>4 squared is 16 Enter a number>5 squared is 25 Enter a number>6 squared is 36 Enter a number>7 squared is 49 Enter a number>8 squared is 64 Enter a number>9 squared is 81 Enter a number>10 squared is 100 Enter a number>Bye
python teststream.py < input.txt > output.txt type output.txt D:\Python33>type output.txt Hello stream world Enter a number>1 squared is 1 Enter a number>2 squared is 4 Enter a number>3 squared is 9 Enter a number>4 squared is 16 Enter a number>5 squared is 25 Enter a number>6 squared is 36 Enter a number>7 squared is 49 Enter a number>8 squared is 64 Enter a number>9 squared is 81 Enter a number>10 squared is 100 Enter a number>Bye
一个python script的输出可以作为另一个python script的输入。
for example 2:
C:\...\PP4E\System\Streams> type writer.py
print("Help! Help! I‘m being repressed!")
print(42)
C:\...\PP4E\System\Streams> type reader.py
print(‘Got this: "%s"‘ % input())
import sys
data = sys.stdin.readline()[:-1]
print(‘The meaning of life is‘, data, int(data) * 2)
C:\...\PP4E\System\Streams> python writer.py
Help! Help! I‘m being repressed!
42
C:\...\PP4E\System\Streams> python writer.py | python reader.py
Got this: "Help! Help! I‘m being repressed!"
The meaning of life is 42 84
fot example 3:
type sort.py import sys # or sorted(sys.stdin) lines = sys.stdin.readlines() # sort stdin input lines, lines.sort() # send result to stdout for line in lines: print(line, end=‘‘) # for further processing type adder.py import sys sum = 0 while True: try: line = input() # or call sys.stdin.readlines() except EOFError: # or for line in sys.stdin: break # input strips \n at end else: sum += int(line) # was sting.atoi() in 2nd ed print(sum) type data.txt 123 000 999 042 python sorter.py < data.txt sort a file 000 042 123 python adder.py < data.txt sum file 1164 type data.txt | python adder.py sum type output 1164 type writer2.py for data in (123, 0, 999, 42): print(‘%03d‘ % data) python writer2.py | python sorter.py sort py output 000 042 123 999 writer2.py | sorter.py shorter form ...same output as prior command on Windows... python writer2.py | python sorter.py | python adder.py 1164 999
for example 4:改进后的代码
type sorterSmall.py import sys for line in sorted(sys.stdin): print(line, end=‘‘) type adderSmall.py import sys print(sum(int(line) for line in sys.stdin))
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