Python命令行参数分号循环错误 [英] Python command line argument semicolon-loop error

问题描述

我正在尝试python -mtimeit，所以我放了python -mtimeit "n = 0; while n < 10: pass" 然后出现一个无效的语法错误.与分号和for循环相同.

I was trying out python -mtimeitso I put python -mtimeit "n = 0; while n < 10: pass" Then an invalid syntax error showed up. same with semicolon and for loop.

但是，当我尝试分号并单独循环时.两者都很好.

However, when I try semicolon and loop individually. Both worked fine.

python -c "for i in range(10): print(n)"  
python -c "n = 1; n = 2; print(n)"

为什么会这样，如何在timeit循环中进行测试?非常感谢你！

Why is this so and how can I test while loop in timeit? Thank you very much!

推荐答案

while，for之前不能有分号，它们必须在一行上.如果您查看的是 Python语法:

while, for can't have semicolon before, they need to be on one line. If you looked at Python grammar:

compound_stmt ::=  if_stmt
                   | while_stmt
                   | for_stmt
                   | try_stmt
                   | with_stmt
                   | funcdef
                   | classdef
                   | decorated
suite         ::=  stmt_list NEWLINE | NEWLINE INDENT statement+ DEDENT
statement     ::=  stmt_list NEWLINE | compound_stmt
stmt_list     ::=  simple_stmt (";" simple_stmt)* [";"]

您将看到 compound_stmt 一部分的语句必须为一行独自的.只能用分号分隔的语句是 simple_stmt 组:

you will see that the statements that are part of compound_stmt need to be one one line alone. The only statements that can be separated by semicolon are simple_stmt group:

simple_stmt ::=  expression_stmt
                 | assert_stmt
                 | assignment_stmt
                 | augmented_assignment_stmt
                 | pass_stmt
                 | del_stmt
                 | print_stmt
                 | return_stmt
                 | yield_stmt
                 | raise_stmt
                 | break_stmt
                 | continue_stmt
                 | import_stmt
                 | global_stmt
                 | exec_stmt

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