Mercurial > cpython-lru_cache-weakref
annotate Lib/pdb.doc @ 4566:6403c94de50d legacy-trunk
Added safeguard against failure in __del__.
| author | Guido van Rossum <guido@python.org> |
|---|---|
| date | Wed, 27 Nov 1996 19:39:58 +0000 |
| parents | 1940892d2fe3 |
| children | 35e1a140fe4e |
| rev | line source |
|---|---|
| 653 | 1 The Python Debugger |
| 2 =================== | |
| 3 | |
| 4 To use the debugger in its simplest form: | |
| 5 | |
| 6 >>> import pdb | |
| 7 >>> pdb.run('<a statement>') | |
| 8 | |
| 9 The debugger's prompt is '(Pdb) '. This will stop in the first | |
| 10 function call in <a statement>. | |
| 11 | |
|
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3dac204b74fa
Added post_mortem() and pm() interfaces to pdb and wdb.
Guido van Rossum <guido@python.org>
parents:
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diff
changeset
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12 Alternatively, if a statement terminated with an unhandled exception, |
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3dac204b74fa
Added post_mortem() and pm() interfaces to pdb and wdb.
Guido van Rossum <guido@python.org>
parents:
719
diff
changeset
|
13 you can use pdb's post-mortem facility to inspect the contents of the |
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3dac204b74fa
Added post_mortem() and pm() interfaces to pdb and wdb.
Guido van Rossum <guido@python.org>
parents:
719
diff
changeset
|
14 traceback: |
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3dac204b74fa
Added post_mortem() and pm() interfaces to pdb and wdb.
Guido van Rossum <guido@python.org>
parents:
719
diff
changeset
|
15 |
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3dac204b74fa
Added post_mortem() and pm() interfaces to pdb and wdb.
Guido van Rossum <guido@python.org>
parents:
719
diff
changeset
|
16 >>> <a statement> |
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3dac204b74fa
Added post_mortem() and pm() interfaces to pdb and wdb.
Guido van Rossum <guido@python.org>
parents:
719
diff
changeset
|
17 <exception traceback> |
|
3dac204b74fa
Added post_mortem() and pm() interfaces to pdb and wdb.
Guido van Rossum <guido@python.org>
parents:
719
diff
changeset
|
18 >>> import pdb |
|
3dac204b74fa
Added post_mortem() and pm() interfaces to pdb and wdb.
Guido van Rossum <guido@python.org>
parents:
719
diff
changeset
|
19 >>> pdb.pm() |
|
3dac204b74fa
Added post_mortem() and pm() interfaces to pdb and wdb.
Guido van Rossum <guido@python.org>
parents:
719
diff
changeset
|
20 |
| 653 | 21 The commands recognized by the debugger are listed in the next |
| 22 section. Most can be abbreviated as indicated; e.g., h(elp) means | |
| 23 that 'help' can be typed as 'h' or 'help' (but not as 'he' or 'hel', | |
| 24 nor as 'H' or 'Help' or 'HELP'). Optional arguments are enclosed in | |
| 25 square brackets. | |
| 26 | |
| 27 A blank line repeats the previous command literally. (Except for | |
| 28 'list', where it lists the next 11 lines.) | |
| 29 | |
| 30 Commands that the debugger doesn't recognize are assumed to be Python | |
| 31 statements and are executed in the context of the program being | |
| 32 debugged. Python statements can also be prefixed with an exclamation | |
| 33 point ('!'). This is a powerful way to inspect the program being | |
| 34 debugged; it is even possible to change variables. When an exception | |
| 35 occurs in such a statement, the exception name is printed but the | |
| 36 debugger's state is not changed. | |
| 37 | |
| 38 The debugger is not directly programmable; but it is implemented as a | |
| 39 class from which you can derive your own debugger class, so you can | |
| 40 make as fancy as you like. | |
| 41 | |
| 42 | |
| 43 Debugger commands | |
| 44 ================= | |
| 45 | |
| 46 h(elp) | |
| 47 Without argument, print the list of available commands. | |
| 48 With a command name as argument, print help about that command | |
| 49 (this is currently not implemented). | |
| 50 | |
| 51 w(here) | |
| 52 Print a stack trace, with the most recent frame at the bottom. | |
| 53 An arrow indicates the "current frame", which determines the | |
| 54 context of most commands. | |
| 55 | |
| 56 d(own) | |
| 57 Move the current frame one level down in the stack trace | |
| 58 (to an older frame). | |
| 59 | |
| 60 u(p) | |
| 61 Move the current frame one level up in the stack trace | |
| 62 (to a newer frame). | |
| 63 | |
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1940892d2fe3
Merge alpha100 branch back to main trunk
Guido van Rossum <guido@python.org>
parents:
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diff
changeset
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64 b(reak) [lineno | function] |
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1940892d2fe3
Merge alpha100 branch back to main trunk
Guido van Rossum <guido@python.org>
parents:
1041
diff
changeset
|
65 With a line number argument, set a break there in the current |
|
1940892d2fe3
Merge alpha100 branch back to main trunk
Guido van Rossum <guido@python.org>
parents:
1041
diff
changeset
|
66 file. With a function name, set a break at the entry of that |
|
1940892d2fe3
Merge alpha100 branch back to main trunk
Guido van Rossum <guido@python.org>
parents:
1041
diff
changeset
|
67 function. Without argument, list all breaks. |
| 653 | 68 |
| 69 cl(ear) [lineno] | |
| 70 With a line number argument, clear that break in the current file. | |
| 71 Without argument, clear all breaks (but first ask confirmation). | |
| 72 | |
| 73 s(tep) | |
| 74 Execute the current line, stop at the first possible occasion | |
| 75 (either in a function that is called or in the current function). | |
| 76 | |
| 77 n(ext) | |
| 78 Continue execution until the next line in the current function | |
| 79 is reached or it returns. | |
| 80 | |
| 81 r(eturn) | |
| 82 Continue execution until the current function returns. | |
| 83 | |
| 84 c(ont(inue)) | |
| 85 Continue execution, only stop when a breakpoint is encountered. | |
| 86 | |
| 87 l(ist) [first [,last]] | |
| 88 List source code for the current file. | |
| 89 Without arguments, list 11 lines around the current line | |
| 90 or continue the previous listing. | |
| 91 With one argument, list 11 lines starting at that line. | |
| 92 With two arguments, list the given range; | |
| 93 if the second argument is less than the first, it is a count. | |
| 94 | |
| 95 a(rgs) | |
| 96 Print the argument list of the current function. | |
| 97 | |
| 98 p expression | |
| 99 Print the value of the expression. | |
| 100 | |
| 101 (!) statement | |
| 102 Execute the (one-line) statement in the context of | |
| 103 the current stack frame. | |
| 104 The exclamation point can be omitted unless the first word | |
| 105 of the statement resembles a debugger command. | |
| 106 To assign to a global variable you must always prefix the | |
| 107 command with a 'global' command, e.g.: | |
| 108 (Pdb) global list_options; list_options = ['-l'] | |
| 109 (Pdb) | |
| 110 | |
| 111 q(uit) | |
| 112 Quit from the debugger. | |
| 113 The program being executed is aborted. | |
| 114 | |
| 115 | |
| 116 How it works | |
| 117 ============ | |
| 118 | |
| 119 Some changes were made to the interpreter: | |
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Document sys.settrace().
Guido van Rossum <guido@python.org>
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diff
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120 - sys.settrace(func) sets the global trace function |
| 653 | 121 - there can also a local trace function (see later) |
| 122 | |
| 123 Trace functions have three arguments: (frame, event, arg) | |
| 124 - frame is the current stack frame | |
| 125 - event is a string: 'call', 'line', 'return' or 'exception' | |
| 126 - arg is dependent on the event type | |
| 127 A trace function should return a new trace function or None. | |
| 128 Class methods are accepted (and most useful!) as trace methods. | |
| 129 | |
| 130 The events have the following meaning: | |
| 131 | |
| 132 'call': A function is called (or some other code block entered). | |
| 133 The global trace function is called; | |
| 134 arg is the argument list to the function; | |
| 135 the return value specifies the local trace function. | |
| 136 | |
| 137 'line': The interpreter is about to execute a new line of code | |
| 138 (sometimes multiple line events on one line exist). | |
| 139 The local trace function is called; arg in None; | |
| 140 the return value specifies the new local trace function. | |
| 141 | |
| 142 'return': A function (or other code block) is about to return. | |
| 143 The local trace function is called; | |
| 144 arg is the value that will be returned. | |
| 145 The trace function's return value is ignored. | |
| 146 | |
| 147 'exception': An exception has occurred. | |
| 148 The local trace function is called; | |
| 149 arg is a triple (exception, value, traceback); | |
| 150 the return value specifies the new local trace function | |
| 151 | |
| 152 Note that as an exception is propagated down the chain of callers, an | |
| 153 'exception' event is generated at each level. | |
| 154 | |
| 155 Stack frame objects have the following read-only attributes: | |
| 156 f_code: the code object being executed | |
| 157 f_lineno: the current line number (-1 for 'call' events) | |
| 158 f_back: the stack frame of the caller, or None | |
| 159 f_locals: dictionary containing local name bindings | |
| 160 f_globals: dictionary containing global name bindings | |
| 161 | |
| 162 Code objects have the following read-only attributes: | |
| 163 co_code: the code string | |
| 164 co_names: the list of names used by the code | |
| 165 co_consts: the list of (literal) constants used by the code | |
| 166 co_filename: the filename from which the code was compiled |