列印語句與列印功能
在 Python 2 中, print
是一個宣告:
Python 2.x <= 2.7
print "Hello World"
print # print a newline
print "No newline", # add trailing comma to remove newline
print >>sys.stderr, "Error" # print to stderr
print("hello") # print "hello", since ("hello") == "hello"
print() # print an empty tuple "()"
print 1, 2, 3 # print space-separated arguments: "1 2 3"
print(1, 2, 3) # print tuple "(1, 2, 3)"
在 Python 3 中, print()
是一個函式,帶有常用的關鍵字引數:
Python 3.x >= 3.0
print "Hello World" # SyntaxError
print("Hello World")
print() # print a newline (must use parentheses)
print("No newline", end="") # end specifies what to append (defaults to newline)
print("Error", file=sys.stderr) # file specifies the output buffer
print("Comma", "separated", "output", sep=",") # sep specifies the separator
print("A", "B", "C", sep="") # null string for sep: prints as ABC
print("Flush this", flush=True) # flush the output buffer, added in Python 3.3
print(1, 2, 3) # print space-separated arguments: "1 2 3"
print((1, 2, 3)) # print tuple "(1, 2, 3)"
列印功能具有以下引數:
print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)
sep
是將傳遞給列印的物件分開的東西。例如:
print('foo', 'bar', sep='~') # out: foo~bar
print('foo', 'bar', sep='.') # out: foo.bar
end
是 print 語句的結尾。例如:
print('foo', 'bar', end='!') # out: foo bar!
在非換行結束列印語句後再次列印將列印到同一行:
print('foo', end='~')
print('bar')
# out: foo~bar
注意: 為了將來的相容性, print
函式也可以在 Python 2.6 之後使用; 但是除非禁用了 print
語句的解析,否則不能使用它
from __future__ import print_function
此函式與 Python 3 的格式完全相同,只是它缺少 flush
引數。
有關基本原理,請參閱 PEP 3105 。