1 | """Extract, format and print information about Python stack traces."""
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2 |
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3 | import linecache
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4 | import sys
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5 | import types
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6 |
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7 | __all__ = ['extract_stack', 'extract_tb', 'format_exception',
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8 | 'format_exception_only', 'format_list', 'format_stack',
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9 | 'format_tb', 'print_exc', 'format_exc', 'print_exception',
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10 | 'print_last', 'print_stack', 'print_tb', 'tb_lineno']
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11 |
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12 | def _print(file, str='', terminator='\n'):
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13 | file.write(str+terminator)
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14 |
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15 |
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16 | def print_list(extracted_list, file=None):
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17 | """Print the list of tuples as returned by extract_tb() or
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18 | extract_stack() as a formatted stack trace to the given file."""
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19 | if file is None:
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20 | file = sys.stderr
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21 | for filename, lineno, name, line in extracted_list:
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22 | _print(file,
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23 | ' File "%s", line %d, in %s' % (filename,lineno,name))
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24 | if line:
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25 | _print(file, ' %s' % line.strip())
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26 |
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27 | def format_list(extracted_list):
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28 | """Format a list of traceback entry tuples for printing.
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29 |
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30 | Given a list of tuples as returned by extract_tb() or
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31 | extract_stack(), return a list of strings ready for printing.
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32 | Each string in the resulting list corresponds to the item with the
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33 | same index in the argument list. Each string ends in a newline;
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34 | the strings may contain internal newlines as well, for those items
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35 | whose source text line is not None.
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36 | """
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37 | list = []
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38 | for filename, lineno, name, line in extracted_list:
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39 | item = ' File "%s", line %d, in %s\n' % (filename,lineno,name)
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40 | if line:
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41 | item = item + ' %s\n' % line.strip()
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42 | list.append(item)
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43 | return list
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44 |
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45 |
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46 | def print_tb(tb, limit=None, file=None):
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47 | """Print up to 'limit' stack trace entries from the traceback 'tb'.
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48 |
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49 | If 'limit' is omitted or None, all entries are printed. If 'file'
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50 | is omitted or None, the output goes to sys.stderr; otherwise
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51 | 'file' should be an open file or file-like object with a write()
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52 | method.
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53 | """
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54 | if file is None:
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55 | file = sys.stderr
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56 | if limit is None:
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57 | if hasattr(sys, 'tracebacklimit'):
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58 | limit = sys.tracebacklimit
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59 | n = 0
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60 | while tb is not None and (limit is None or n < limit):
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61 | f = tb.tb_frame
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62 | lineno = tb.tb_lineno
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63 | co = f.f_code
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64 | filename = co.co_filename
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65 | name = co.co_name
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66 | _print(file,
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67 | ' File "%s", line %d, in %s' % (filename, lineno, name))
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68 | linecache.checkcache(filename)
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69 | line = linecache.getline(filename, lineno, f.f_globals)
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70 | if line: _print(file, ' ' + line.strip())
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71 | tb = tb.tb_next
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72 | n = n+1
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73 |
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74 | def format_tb(tb, limit = None):
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75 | """A shorthand for 'format_list(extract_tb(tb, limit))'."""
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76 | return format_list(extract_tb(tb, limit))
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77 |
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78 | def extract_tb(tb, limit = None):
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79 | """Return list of up to limit pre-processed entries from traceback.
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80 |
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81 | This is useful for alternate formatting of stack traces. If
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82 | 'limit' is omitted or None, all entries are extracted. A
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83 | pre-processed stack trace entry is a quadruple (filename, line
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84 | number, function name, text) representing the information that is
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85 | usually printed for a stack trace. The text is a string with
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86 | leading and trailing whitespace stripped; if the source is not
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87 | available it is None.
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88 | """
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89 | if limit is None:
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90 | if hasattr(sys, 'tracebacklimit'):
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91 | limit = sys.tracebacklimit
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92 | list = []
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93 | n = 0
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94 | while tb is not None and (limit is None or n < limit):
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95 | f = tb.tb_frame
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96 | lineno = tb.tb_lineno
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97 | co = f.f_code
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98 | filename = co.co_filename
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99 | name = co.co_name
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100 | linecache.checkcache(filename)
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101 | line = linecache.getline(filename, lineno, f.f_globals)
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102 | if line: line = line.strip()
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103 | else: line = None
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104 | list.append((filename, lineno, name, line))
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105 | tb = tb.tb_next
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106 | n = n+1
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107 | return list
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108 |
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109 |
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110 | def print_exception(etype, value, tb, limit=None, file=None):
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111 | """Print exception up to 'limit' stack trace entries from 'tb' to 'file'.
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112 |
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113 | This differs from print_tb() in the following ways: (1) if
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114 | traceback is not None, it prints a header "Traceback (most recent
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115 | call last):"; (2) it prints the exception type and value after the
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116 | stack trace; (3) if type is SyntaxError and value has the
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117 | appropriate format, it prints the line where the syntax error
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118 | occurred with a caret on the next line indicating the approximate
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119 | position of the error.
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120 | """
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121 | if file is None:
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122 | file = sys.stderr
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123 | if tb:
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124 | _print(file, 'Traceback (most recent call last):')
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125 | print_tb(tb, limit, file)
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126 | lines = format_exception_only(etype, value)
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127 | for line in lines:
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128 | _print(file, line, '')
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129 |
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130 | def format_exception(etype, value, tb, limit = None):
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131 | """Format a stack trace and the exception information.
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132 |
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133 | The arguments have the same meaning as the corresponding arguments
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134 | to print_exception(). The return value is a list of strings, each
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135 | ending in a newline and some containing internal newlines. When
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136 | these lines are concatenated and printed, exactly the same text is
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137 | printed as does print_exception().
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138 | """
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139 | if tb:
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140 | list = ['Traceback (most recent call last):\n']
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141 | list = list + format_tb(tb, limit)
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142 | else:
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143 | list = []
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144 | list = list + format_exception_only(etype, value)
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145 | return list
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146 |
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147 | def format_exception_only(etype, value):
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148 | """Format the exception part of a traceback.
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149 |
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150 | The arguments are the exception type and value such as given by
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151 | sys.last_type and sys.last_value. The return value is a list of
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152 | strings, each ending in a newline.
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153 |
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154 | Normally, the list contains a single string; however, for
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155 | SyntaxError exceptions, it contains several lines that (when
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156 | printed) display detailed information about where the syntax
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157 | error occurred.
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158 |
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159 | The message indicating which exception occurred is always the last
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160 | string in the list.
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161 |
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162 | """
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163 |
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164 | # An instance should not have a meaningful value parameter, but
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165 | # sometimes does, particularly for string exceptions, such as
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166 | # >>> raise string1, string2 # deprecated
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167 | #
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168 | # Clear these out first because issubtype(string1, SyntaxError)
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169 | # would raise another exception and mask the original problem.
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170 | if (isinstance(etype, BaseException) or
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171 | isinstance(etype, types.InstanceType) or
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172 | etype is None or type(etype) is str):
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173 | return [_format_final_exc_line(etype, value)]
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174 |
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175 | stype = etype.__name__
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176 |
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177 | if not issubclass(etype, SyntaxError):
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178 | return [_format_final_exc_line(stype, value)]
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179 |
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180 | # It was a syntax error; show exactly where the problem was found.
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181 | lines = []
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182 | try:
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183 | msg, (filename, lineno, offset, badline) = value.args
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184 | except Exception:
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185 | pass
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186 | else:
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187 | filename = filename or "<string>"
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188 | lines.append(' File "%s", line %d\n' % (filename, lineno))
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189 | if badline is not None:
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190 | lines.append(' %s\n' % badline.strip())
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191 | if offset is not None:
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192 | caretspace = badline.rstrip('\n')
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193 | offset = min(len(caretspace), offset) - 1
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194 | caretspace = caretspace[:offset].lstrip()
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195 | # non-space whitespace (likes tabs) must be kept for alignment
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196 | caretspace = ((c.isspace() and c or ' ') for c in caretspace)
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197 | lines.append(' %s^\n' % ''.join(caretspace))
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198 | value = msg
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199 |
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200 | lines.append(_format_final_exc_line(stype, value))
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201 | return lines
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202 |
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203 | def _format_final_exc_line(etype, value):
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204 | """Return a list of a single line -- normal case for format_exception_only"""
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205 | valuestr = _some_str(value)
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206 | if value is None or not valuestr:
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207 | line = "%s\n" % etype
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208 | else:
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209 | line = "%s: %s\n" % (etype, valuestr)
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210 | return line
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211 |
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212 | def _some_str(value):
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213 | try:
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214 | return str(value)
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215 | except Exception:
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216 | pass
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217 | try:
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218 | value = unicode(value)
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219 | return value.encode("ascii", "backslashreplace")
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220 | except Exception:
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221 | pass
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222 | return '<unprintable %s object>' % type(value).__name__
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223 |
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224 |
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225 | def print_exc(limit=None, file=None):
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226 | """Shorthand for 'print_exception(sys.exc_type, sys.exc_value, sys.exc_traceback, limit, file)'.
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227 | (In fact, it uses sys.exc_info() to retrieve the same information
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228 | in a thread-safe way.)"""
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229 | if file is None:
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230 | file = sys.stderr
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231 | try:
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232 | etype, value, tb = sys.exc_info()
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233 | print_exception(etype, value, tb, limit, file)
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234 | finally:
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235 | etype = value = tb = None
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236 |
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237 |
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238 | def format_exc(limit=None):
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239 | """Like print_exc() but return a string."""
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240 | try:
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241 | etype, value, tb = sys.exc_info()
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242 | return ''.join(format_exception(etype, value, tb, limit))
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243 | finally:
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244 | etype = value = tb = None
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245 |
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246 |
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247 | def print_last(limit=None, file=None):
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248 | """This is a shorthand for 'print_exception(sys.last_type,
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249 | sys.last_value, sys.last_traceback, limit, file)'."""
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250 | if not hasattr(sys, "last_type"):
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251 | raise ValueError("no last exception")
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252 | if file is None:
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253 | file = sys.stderr
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254 | print_exception(sys.last_type, sys.last_value, sys.last_traceback,
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255 | limit, file)
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256 |
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257 |
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258 | def print_stack(f=None, limit=None, file=None):
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259 | """Print a stack trace from its invocation point.
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260 |
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261 | The optional 'f' argument can be used to specify an alternate
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262 | stack frame at which to start. The optional 'limit' and 'file'
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263 | arguments have the same meaning as for print_exception().
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264 | """
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265 | if f is None:
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266 | try:
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267 | raise ZeroDivisionError
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268 | except ZeroDivisionError:
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269 | f = sys.exc_info()[2].tb_frame.f_back
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270 | print_list(extract_stack(f, limit), file)
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271 |
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272 | def format_stack(f=None, limit=None):
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273 | """Shorthand for 'format_list(extract_stack(f, limit))'."""
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274 | if f is None:
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275 | try:
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276 | raise ZeroDivisionError
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277 | except ZeroDivisionError:
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278 | f = sys.exc_info()[2].tb_frame.f_back
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279 | return format_list(extract_stack(f, limit))
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280 |
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281 | def extract_stack(f=None, limit = None):
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282 | """Extract the raw traceback from the current stack frame.
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283 |
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284 | The return value has the same format as for extract_tb(). The
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285 | optional 'f' and 'limit' arguments have the same meaning as for
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286 | print_stack(). Each item in the list is a quadruple (filename,
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287 | line number, function name, text), and the entries are in order
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288 | from oldest to newest stack frame.
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289 | """
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290 | if f is None:
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291 | try:
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292 | raise ZeroDivisionError
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293 | except ZeroDivisionError:
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294 | f = sys.exc_info()[2].tb_frame.f_back
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295 | if limit is None:
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296 | if hasattr(sys, 'tracebacklimit'):
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297 | limit = sys.tracebacklimit
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298 | list = []
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299 | n = 0
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300 | while f is not None and (limit is None or n < limit):
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301 | lineno = f.f_lineno
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302 | co = f.f_code
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303 | filename = co.co_filename
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304 | name = co.co_name
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305 | linecache.checkcache(filename)
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306 | line = linecache.getline(filename, lineno, f.f_globals)
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307 | if line: line = line.strip()
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308 | else: line = None
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309 | list.append((filename, lineno, name, line))
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310 | f = f.f_back
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311 | n = n+1
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312 | list.reverse()
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313 | return list
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314 |
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315 | def tb_lineno(tb):
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316 | """Calculate correct line number of traceback given in tb.
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317 |
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318 | Obsolete in 2.3.
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319 | """
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320 | return tb.tb_lineno
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